µ-LED, µ-LED DEVICE, DISPLAY AND METHOD FOR THE SAME

ABSTRACT

Disclosed are various aspects of a μ-LED or a μ-LED array for augmented reality or lighting applications, in particular in the automotive field. The μ-LED is characterized by particularly small dimensions in the range of a few μm.

This patent application is a continuation of U.S. application Ser. No.17/039,097 filed Sep. 30, 2020, which claims the priorities of theGerman applications DE 10 2019 116 313.7 of 14 Jun. 2019, DE 10 2019 118251.4 of 5 Jul. 2019, DE 10 2019 112 616.9 of 14 May 2019, DE 10 2019110 499.8 of 23 Apr. 2019, DE 10 2019 112 639.8 of 14 May 2019, DE 102019 115 991.1 of 12 Jun. 2019, as well as the priority of the Danishapplication DK PA201970059 of 29 Jan. 2019, the disclosure of which areincorporated herein by way of reference. Finally, this application alsoclaims priority from the PCT application PCT/EP2020/052191 of 29 Jan.2020. The disclosure of PCT/EP2020/052191 is incorporated herein byreference in its entirety. Additionally, this patent application isrelated to the following co-pending patent applications: U.S.application Ser. No. 17/038,283, entitled “μ-LED, μ-LED Device, Displayand Method for the Same,” filed Sep. 30, 2020; U.S. application Ser. No.17/039,283, entitled “μ-LED, μ-LED Device, Display and Method for theSame,” filed Sep. 30, 2020; U.S. application Ser. No. 17/039,482,entitled “μ-LED, μ-LED Device, Display and Method for the Same,” filedSep. 30, 2020; U.S. application Ser. No. 17/475,030, entitled “μ-LED,μ-LED Device, Display and Method for the Same,” filed Sep. 14, 2021;U.S. application Ser. No. 17/474,975, entitled “μ-LED, μ-LED Device,Display and Method for the Same,” filed Sep. 14, 2021; U.S. applicationSer. No. 17/510,907, entitled “μ-LED, μ-LED Device, Display and Methodfor the Same,” filed Oct. 26, 2021; U.S. application Ser. No. ______(Ref. OS01P201WOC3USC4), entitled “μ-LED, μ-LED Device, Display andMethod for the Same,” filed Oct. 28, 2021; and U.S. application Ser. No.______ (Ref. OS01P201WOC3USC2), entitled “μ-LED, μ-LED Device, Displayand Method for the Same,” filed Oct. 28, 2021.

BACKGROUND

The ongoing current developments within the Internet of Things and thefield of communication have opened the door for various new applicationsand concepts. For development, service and manufacturing purposes, theseconcepts and applications offer increased effectiveness and efficiency.

One aspect of new concepts is based on augmented or virtual reality. Ageneral definition of “augmented reality” is given by an “interactiveexperience of the real environment, whereby the objects from it, whichare in the real world, are augmented by computer generated perceptibleinformation”.

The information is mostly transported by visualization, but is notlimited to visual perception. Sometimes haptic or other sensoryperceptions can be used to expand reality. In the case of visualization,the superimposed sensory-visual information can be constructive, i.e.additional to the natural environment, or it can be destructive, forexample by obscuring parts of the natural environment. In someapplications, it is also possible to interact with the superimposedsensory information in one way or another. In this way, augmentedreality reinforces the ongoing perception of the user of the realenvironment.

In contrast, “virtual reality” completely replaces the real environmentof the user with an environment that is completely simulated. In otherwords, while in an augmented reality environment the user is able toperceive the real world at least partially, in a virtual reality theenvironment is completely simulated and may differ significantly fromreality.

Augmented Reality can be used to improve natural environmentalsituations, enriching the user's experience or supporting the user inperforming certain tasks. For example, a user may use a display withaugmented reality features to assist him in performing certain tasks.Because information about a real object is superimposed to provide cluesto the user, the user is supported with additional information, allowingthe user to act more quickly, safely and effectively duringmanufacturing, repair or other services. In the medical field, augmentedreality can be used to guide and support the doctor in diagnosing andtreating the patient. In development, an engineer may experience theresults of his experiments directly and can therefore evaluate theresults more easily. In the tourism or event industry, augmented realitycan provide a user with additional information about sights, history,and the like. Augmented Reality can support the learning of activitiesor tasks.

SUMMARY

In the following summary different aspects for μ-displays in theautomotive and augmented reality applications are explained. Thisincludes devices, displays, controls, process engineering methods andother aspects suitable for augmented reality and automotiveapplications. This includes aspects which are directed to lightgeneration by means of displays, indicators or similar. In addition,control circuits, power supplies and aspects of light extraction, lightguidance and focusing as well as applications of such devices are listedand explained by means of various examples.

Because of the various limitations and challenges posed by the smallsize of the light-generating components, a combination of the variousaspects is not only advantageous, but often necessary. For ease ofreference, this disclosure is divided into several sections with similartopics. However, this should explicitly not be understood to mean thatfeatures from one topic can not be combined with others. Rather, aspectsfrom different topics should be combined to create a display foraugmented reality or other applications or even in the automotivesector.

For considerations of the following solutions, some terms andexpressions should be explained in order to define a common and equalunderstanding. The terms listed are generally used with thisunderstanding in this document. In individual cases, however, there maybe deviations from the interpretation, whereby such deviation will bespecifically referred to.

“Active Matrix Display”

The term “active matrix display” was originally used for liquid crystaldisplays containing a matrix of thin film transistors that drive LCDpixels. Each individual pixel has a circuit with active components(usually transistors) and power supply connections. At present, however,this technology should not be limited to liquid crystals, but shouldalso be used in particular for driving μ-LEDs or μ-displays.

“Active Matrix Carrier Substrate”

“Active matrix carrier substrate” or “active matrix backplane” means adrive for light emitting diodes of a display with thin-film transistorcircuits. The circuits may be integrated into the backplane or mountedon it. The “active matrix carrier substrate” has one or more interfacecontacts, which form an electrical connection to a μ-LED displaystructure. An “active-matrix carrier substrate” can thus be part of anactive-matrix display or support it.

“Active Layer”

The active layer is referred to as the layer in an optoelectroniccomponent or light emitting diode in which charge carriers recombine. Inits simplest form, the active layer can be characterized by a region oftwo adjacent semiconductor layers of different conductivity type. Morecomplex active layers comprise quantum wells (see there), multi-quantumwells or other structures that have additional properties. Similarly,the structure and material systems can be used to adjust the band gap(see there) in the active layer, which determines the wavelength andthus the color of the light.

“Alvarez Lens Array”

With the use of Alvarez lens pairs, a beam path can be adapted to videoeyewear. An adjustment optic comprises an Alvarez lens arrangement, inparticular a rotatable version with a Moire lens arrangement. Here, thebeam deflection is determined by the first derivative of the respectivephase plate relief, which is approximated, for example, byz=ax2+by2+cx+dy+e for the transmission direction z and the transversedirections x and y, and by the offset of the two phase plates arrangedin pairs in the transverse directions x and y. For further designalternatives, swivelling prisms are provided in the adjustment optics.

“Augmented Reality (AR)”

This is an interactive experience of the real environment, where thesubject of the picking up is located in the real world and is enhancedby computer-generated perceptible information. Extended reality is thecomputer-aided extension of the perception of reality by means of thiscomputer-generated perceptible information. The information can addressall human sensory modalities. Often, however, augmented reality is onlyunderstood to be the visual representation of information, i.e. thesupplementation of images or videos with computer-generated additionalinformation or virtual objects by means of fade-in/overlay. Applicationsand explanations of the mode of operation of Augmented Reality can befound in the introduction and in the following in execution examples.

“Automotive.”

Automotive generally refers to the motor vehicle or automobile industry.This term should therefore cover this branch, but also all otherbranches of industry which include μ-displays or generally lightdisplays—with very high resolution and μ-LEDs.

“Bandgap”

Bandgap, also known as band gap or forbidden zone, is the energeticdistance between the valence band and conduction band of a solid-statebody. Its electrical and optical properties are largely determined bythe size of the band gap. The size of the band gap is usually specifiedin electron volts (eV). The band gap is thus also used to differentiatebetween metals, semiconductors and insulators. The band gap can beadapted, i.e. changed, by various measures such as spatial doping,deforming of the crystal lattice structure or by changing the materialsystems. Material systems with so-called direct band gap, i.e. where themaximum of the valence band and a minimum of the conduction band in thepulse space are superimposed, allow a recombination of electron-holepairs under emission of light.

“Bragg Grid”

Fibre Bragg gratings are special optical interference filters inscribedin optical fibres. Wavelengths that lie within the filter bandwidtharound AB are reflected. In the fiber core of an optical waveguide, aperiodic modulation of the refractive index is generated by means ofvarious methods. This creates areas with high and low refractive indexesthat reflect light of a certain wavelength (bandstop). The centerwavelength of the filter bandwidth in single-mode fibers results fromthe Bragg condition.

“Directionality”

Directionality is the term used to describe the radiation pattern of aμ-LED or other light-emitting device. A high directionality correspondsto a high directional radiation, or a small radiation cone. In general,the aim should be to obtain a high directional radiation so thatcrosstalk of light into adjacent pixels is avoided as far as possible.Accordingly, the light-emitting component has a different brightnessdepending on the viewing angle and thus differs from a Lambert emitter.

The directionality can be changed by mechanical measures or othermeasures, for example on the side intended for the emission. In additionto lenses and the like, this includes photonic crystals or pillarstructures (columnar structures) arranged on the emitting surface of apixelated array or on an arrangement of, in particular, μ-LEDs. Thesegenerate a virtual band gap that reduces or prevents the propagation ofa light vector along the emitting surface.

“Far Field”

The terms near field and far field describe spatial areas around acomponent emitting an electromagnetic wave, which differ in theircharacterization. Usually the space regions are divided into threeareas: reactive near field, transition field and far field. In the farfield, the electromagnetic wave propagates as a plane wave independentof the radiating element.

“Fly Screen Effect”

The Screen Door Effect (SDE) is a permanently visible image artefact indigital video projectors. The term fly screen effect describes theunwanted black space between the individual pixels or their projectedinformation, which is caused by technical reasons, and takes the form ofa fly screen. This distance is due to the construction, because betweenthe individual LCD segments run the conductor paths for control, wherelight is swallowed and therefore cannot hit the screen. If smalloptoelectronic lighting devices and especially μ-LEDs are used or if thedistance between individual light emitting diodes is too great, theresulting low packing density leads to possibly visible differencesbetween pointy illuminated and dark areas when viewing a single pixelarea. This so-called fly screen effect (screen door effect) isparticularly noticeable at a short viewing distance and thus especiallyin applications such as VR glasses. Sub-pixel structures are usuallyperceived and perceived as disturbing when the illumination differencewithin a pixel continues periodically across the matrix arrangement.Accordingly, the fly screen effect in automotive and augmented realityapplications should be avoided as far as possible.

“Flip Chip”

Flip-chip assembly is a process of assembly and connection technologyfor contacting unpackaged semiconductor chips by means of contact bumps,or short “bumps”. In flip-chip mounting, the chip is mounted directly,without any further connecting wires, with the active contacting sidedown—towards the substrate/circuit carrier—via the bumps. This resultsin particularly small package dimensions and short conductor lengths. Aflip-chip is thus in particular an electronic semiconductor componentcontacted on its rear side. The mounting may also require specialtransfer techniques, for example using an auxiliary carrier. Theradiation direction of a flip chip is then usually the side opposite thecontact surfaces.

“Flip-Flop”

A flip-flop, often called a bi-stable flip-flop or bi-stable flip-flopelement, is an electronic circuit that has two stable states of theoutput signal. The current state depends not only on the input signalspresent at the moment, but also on the state that existed prior to thetime under consideration. A dependence on time does not exist, but onlyon events. Due to the bi-stability, the flip-flop can store a dataquantity of a single bit for an unlimited time. In contrast to othertypes of storage, however, power supply must be permanently guaranteed.The flip-flop, as the basic component of sequential circuits, is anindispensable component of digital technology and thus a fundamentalcomponent of many electronic circuits, from quartz watches tomicroprocessors. In particular, as an elementary one-bit memory, it isthe basic element of static memory components for computers. Somedesigns can use different types of flip-flops or other buffer circuitsto store state information. Their respective input and output signalsare digital, i.e. they alternate between logical “false” and logical“true”. These values are also known as “low” 0 and “high” 1.

“Head-Up Display”

The head-up display is a display system or projection device that allowsusers to maintain their head position or viewing direction by projectinginformation into their field of vision. The Head-up Display is anaugmented reality system. In some cases, a Head-Up Display has a sensorto determine the direction of vision or orientation in space.

“Horizontal Light Emitting Diode”

With horizontal LEDs, the electrical connections are on a common side ofthe LED. This is often the back of the LED facing away from the lightemission surface. Horizontal LEDs therefore have contacts that are onlyformed on one surface side.

“Interference Filter”

Interference filters are optical components that use the effect ofinterference to filter light according to frequency, i.e. color forvisible light.

“Collimation”

In optics, collimation refers to the parallel direction of divergentlight beams. The corresponding lens is called collimator or convergentlens. A collimated light beam contains a large proportion of parallelrays and is therefore minimally spread when it spreads. A use in thissense refers to the spreading of light emitted by a source. A collimatedbeam emitted from a surface has a strong dependence on the angle ofradiation. In other words, the radiance (power per unit of a fixed angleper unit of projected source area) of a collimated light source changeswith increasing angle. Light can be collimated by a number of methods,for example by using a special lens placed in front of the light source.Consequently, collimated light can also be considered as light with avery high directional dependence.

“Converter Material”

Converter material is a material, which is suitable for converting lightof a first wavelength into a second wavelength. The first wavelength isshorter than the second wavelength. This includes various stableinorganic as well as organic dyes and quantum dots. The convertermaterial can be applied and structured in various processes.

“Lambert Lamps”

For many applications, a so-called Lambertian radiation pattern isrequired. This means that a light-emitting surface ideally has a uniformradiation density over its area, resulting in a vertically circulardistribution of radiant intensity. Since the human eye only evaluatesthe luminance (luminance is the photometric equivalent of radiance),such a Lambertian material appears to be equally bright regardless ofthe direction of observation. Especially for curved and flexible displaysurfaces, this uniform, angle-independent brightness can be an importantquality factor that is sometimes difficult to achieve with currentlyavailable displays due to their design and LED technology.

LEDs and μ-LEDs resemble a Lambert spotlight and emit light in a largespatial angle. Depending on the application, further measures are takento improve the radiation characteristics or to achieve greaterdirectionality (see there).

“Conductivity Type”

The term “conductivity type” refers to the majority of (n- or p-) chargecarriers in a given semiconductor material. In other words, asemiconductor material that is n-doped is considered to be of n-typeconductivity. Accordingly, if a semiconductor material is n-type, thenit is n-doped. The term “active” region in a semiconductor refers to aborder region in a semiconductor between an n-doped layer and a p-dopedlayer. In this region, a radiative recombination of p- and n-type chargecarriers takes place. In some designs, the active region is stillstructured and includes, for example, quantum well or quantum dotstructures.

“Light Field Display”

Virtual retinal display (VNA) or light field display is referred to adisplay technology that draws a raster image directly onto the retina ofthe eye. The user gets the impression of a screen floating in front ofhim. A light field display can be provided in the form of glasses,whereby a raster image is projected directly onto the retina of a user'seye. In the virtual retina display, a direct retinal projection createsan image within the user's eye. The light field display is an augmentedreality system.

“Lithography” or “Photolithography”

Photolithography is one of the central methods of semiconductor andmicrosystem technology for the production of integrated circuits andother products. The image of a photomask is transferred onto aphotosensitive photoresist by means of exposure. Afterwards, the exposedareas of the photoresist are dissolved (alternatively, the unexposedareas can be dissolved if the photoresist is cured under light). Thiscreates a lithographic mask that allows further processing by chemicaland physical processes, such as applying material to the open areas oretching depressions in the open areas. Later, the remaining photoresistcan also be removed.

“μ-LED”

A μ-LED is an optoelectronic component whose edge lengths are less than70 μm, especially down to less than 20 μm, especially in the range of 1μm to 10 μm. Another range is between 10 to 30 μm. This results in anarea of a few hundred μm² down to several tens of μm². For example, aμ-LED can comprise an area of about 60 μm² with an edge length of about8 μm. In some cases, a μ-LED has an edge length of 5 μm or less,resulting in a size of less than 30 μm². Typical heights of such μ-LEDsare, for example, in the range of 1.5 μm to 10 μm.

In addition to classic lighting applications, displays are the mainapplications for μ-LEDs. The μ-LEDs form pixels or subpixels and emitlight of a defined color. Due to their small pixel size and high densitywith a small pitch, μ-LEDs are suitable for small monolithic displaysfor AR applications, among other things.

Due to the above-mentioned very small size of a μ-LED, the productionand processing is significantly more difficult compared to previouslarger LEDs. The same applies to additional elements such as contacts,package, lenses etc. Some aspects that can be realized with largeroptoelectronic components cannot be produced with μ-LEDs or only in adifferent way. In this respect, a μ-LED is therefore significantlydifferent from a conventional LED, i.e. a light emitting device with anedge length of 200 μm or more.

“μ-LED Array”

See at μ-display

“μ-Display”

A μ-display or μ-LED array is a matrix with a plurality of pixelsarranged in defined rows and columns. With regard to its functionality,a μ-LED array often forms a matrix of μ-LEDs of the same type and color.Therefore, it rather provides a lighting surface. The purpose of aμ-display, on the other hand, is to transmit information, which oftenresults in the demand for different colors or an addressable control foreach individual pixel or subpixel. A μ-display can be made up of severalμ-LED arrays, which are arranged together on a backplane or othercarrier. Likewise, a μ-LED array can also form a μ-Display.

The size of each pixel is in the order of a few μm, similar to μ-LEDs.Consequently, the overall dimension of a p display with 1920*1080 pixelswith a μ-LED size of 5 μm per pixel and directly adjacent pixels is inthe order of a few 10 mm². In other words, a μ-display or μ-LED array isa small-sized arrangement, which is realized by means of μ-LEDs.

μ-displays or μ-LED arrays can be formed from the same, i.e. from onework piece. The μ-LEDs of the μ-LED array can be monolithic. Suchμ-displays or μ-LED arrays are called monolithic μ-LED arrays orμ-displays.

Alternatively, both assemblies can be formed by growing μ-LEDsindividually on a substrate and then arranging them individually or ingroups on a carrier at a desired distance from each other using aso-called Pick & Place process. Such μ-displays or μ-LED arrays arecalled non-monolithic. For non-monolithic ρ-displays or μ-LED arrays,other distances between individual μ-LEDs are also possible. Thesedistances can be chosen flexibly depending on the application anddesign. Thus, such μ-displays or μ-LED arrays can also be calledpitch-expanded. In the case of pitch-expanded μ-displays or μ-LEDarrays, this means that the μ-LEDs are arranged at a greater distancethan on the growth substrate when transferred to a carrier. In anon-monolithic μ-display or μ-LED array, each individual pixel cancomprise a blue light-emitting μ-LED and a green light-emitting μ-LED aswell as a red light-emitting μ-LED.

To take advantage of different advantages of monolithic μ-LED arrays andnon-monolithic μ-LED arrays in a single module, monolithic μ-LED arrayscan be combined with non-monolithic μ-LED arrays in a μ-display. Thus,μ-displays can be used to realize different functions or applications.Such a display is called a hybrid display.

“μ-LED Nano Column”

A μ-LED nano column is generally a stack of semiconductor layers with anactive layer, thus forming a μ-LED. The μ-LED nano column has an edgelength smaller than the height of the column. For example, the edgelength of a μ-LED nanopillar is approximately 10 nm to 300 nm, while theheight of the device can be in the range of 200 nm to 1 μm or more.

“μ-Rod”

μ-rod or Rod designates in particular a geometric structure, inparticular a rod or bar or generally a longitudinally extending, forexample cylindrical, structure. μ-rods are produced with spatialdimensions in the μm to nanometer range. Thus, nanorods are alsoincluded here.

“Nanorods”

In nanotechnology, nanorods are a design of nanoscale objects. Each oftheir dimensions is in the range of about 10 nm to 500 nm. They may besynthesized from metal or semiconducting materials. Aspect ratios(length divided by width) are 3 to 5. Nanorods are produced by directchemical synthesis. A combination of ligands acts as a shape controlagent and attaches to different facets of the nanorod with differentstrengths. This allows different shapes of the nanorod with differentgrowth rates to produce an elongated object. μ-LED nanopillars are suchnanorods.

“Miniature LED”

Their dimensions range from 100 μm to 750 μm, especially in the rangelarger than 150 μm.

“Moiré Effect” and “Moiré Lens Arrangement”

The moiré effect refers to an apparent coarse raster that is created byoverlaying regular, finer rasters. The resulting pattern, whoseappearance is similar to patterns resulting from interference, is aspecial case of the aliasing effect by subsampling. In the field ofsignal analysis, aliasing effects are errors that occur when the signalto be sampled contains frequency components that are higher than halfthe sampling frequency. In image processing and computer graphics,aliasing effects occur when images are scanned and result in patternsthat are not included in the original image. A moire lens array is aspecial case of an Alvarez lens array.

“Monolithic Construction Element”

A monolithic construction element is a construction element made of onepiece. A typical such device is for example a monolithic pixel array,where the array is made of one piece and the μ-LEDs of the array aremanufactured together on one carrier.

“Optical Mode”

A mode is the description of certain temporally stationary properties ofa wave. The wave is described as the sum of different modes. The modesdiffer in the spatial distribution of the intensity. The shape of themodes is determined by the boundary conditions under which the wavepropagates. The analysis according to vibration modes can be applied toboth standing and continuous waves. For electromagnetic waves, such aslight, laser and radio waves, the following types of modes aredistinguished: TEM or transverse electromagnetic mode, TE or H modes, TMor E modes. TEM or transverse electromagnetic mode: Both the electricand the magnetic field components are always perpendicular to thedirection of propagation. This mode is only propagation-capable ifeither two conductors (equipotential surfaces) insulated from each otherare available, for example in a coaxial cable, or no electricalconductor is available, for example in gas lasers or optical fibers. TEor H modes: Only the electric field component is perpendicular to thedirection of propagation, while the magnetic field component is in thedirection of propagation. TM or E modes: Only the magnetic fieldcomponent is perpendicular to the propagation direction, while theelectric field component points in the propagation direction.

“Optoelectronic Device”

An optoelectronic component is a semiconductor body that generates lightby recombination of charge carriers during operation and emits it. Thelight generated can range from the infrared to the ultraviolet range,with the wavelength depending on various parameters, including thematerial system used and doping. An optoelectronic component is alsocalled a light emitting diode.

For the purpose of this disclosure, the term optoelectronic device oralso light-emitting device is used synonymously. A PLED (see there) isthus a special optoelectronic device with regard to its geometry. Indisplays, optoelectronic components are usually monolithic or asindividual components placed on a matrix.

“Passive matrix backplane” or “passive matrix carrier substrate” Apassive matrix display is a matrix display, in which the individualpixels are driven passively (without additional electronic components inthe individual pixels). A light emitting diode of a display can becontrolled by means of IC circuits. In contrast, displays with activepixels driven by transistors are referred to as active matrix displays.A passive matrix carrier substrate is part of a passive matrix displayand carries it.

“Photonic Crystal” or “Photonic Structure”

A photonic structure can be a photonic crystal, a quasi-periodic ordeterministically aperiodic photonic structure. The photonic structuregenerates a band structure for photons by a periodic variation of theoptical refractive index. This band structure can comprise a band gap ina certain frequency range. As a result, photons cannot propagate throughthe photonic structure in all spatial directions. In particular,propagation parallel to a surface is often blocked, but perpendicular toit is possible. In this way, the photonic structure or the photoniccrystal determines a propagation in a certain direction. It blocks orreduces this in one direction and thus generates a beam or a bundle ofrays of radiation directed as required into the room or radiation areaprovided for this purpose.

Photonic crystals are photonic structures occurring or created intransparent solids. Photonic crystals are not necessarilycrystalline—their name derives from analogous diffraction and reflectioneffects of X-rays in crystals due to their lattice constants. Thestructure dimensions are equal to or greater than a quarter of thecorresponding wavelength of the photons, i.e. they are in the range offractions of a μm to several μm. They are produced by classicallithography or also by self-organizing processes.

Similar or the same property of a photonic crystal can alternatively beproduced with non-periodic but nevertheless ordered structures. Suchstructures are especially quasiperiodic structures or deterministicallyaperiodic structures. These can be for example spiral photonicarrangements.

In particular, so-called two-dimensional photonic crystals are mentionedhere as examples, which exhibit a periodic variation of the opticalrefractive index in two mutually perpendicular spatial directions,especially in two spatial directions parallel to the light-emittingsurface and perpendicular to each other.

However, there are also one-dimensional photonic structures, especiallyone-dimensional photonic crystals. A one-dimensional photonic crystalexhibits a periodic variation of the refractive index along onedirection. This direction can be parallel to the light exit plane. Dueto the one-dimensional structure, a beam can be formed in a firstspatial direction. Thereby a photonic effect can be achieved alreadywith a few periods in the photonic structure. For example, the photonicstructure can be designed in such a way that the electromagneticradiation is at least approximately collimated with respect to the firstspatial direction. Thus, a collimated beam can be generated at leastwith respect to the first direction in space.

“Pixel”

Pixel, pixel, image cell or picture element refers to the individualcolor values of a digital raster graphic as well as the area elementsrequired to capture or display a color value in an image sensor orscreen with raster control. A pixel is thus an addressable element in adisplay device and comprises at least one light-emitting device. A pixelhas a certain size and adjacent pixels are separated by a defineddistance or pixel space. In displays, especially μ-displays, often three(or in case of additional redundancy several) subpixels of differentcolor are combined to one pixel.

“Planar Array”

A planar array is an essentially flat surface. It is often smooth andwithout protruding structures. Roughness of the surface is usually notdesired and does not have the desired functionality. A planar array isfor example a monolithic, planar array with several optoelectroniccomponents.

“Pulse width modulation” Pulse width modulation or PWM is a type ofmodulation for driving a component, in particular a μ-LED. Here the PWMsignal controls a switch that is configured to switch a current throughthe respective μ-LED on and off so that the μ-LED either emits light ordoes not emit light. With the PWM, the output provides a square wavesignal with a fixed frequency f. The relative quantity of the switch-ontime compared to the switch-off time during each period T (=1/f)determines the brightness of the light emitted by the μ-LED. The longerthe switch-on time, the brighter the light.

“Quantum Well”

A quantum well or quantum well refers to a potential in a band structurein one or more semiconductor materials that restricts the freedom ofmovement of a particle in a spatial dimension (usually in thez-direction). As a result, only one planar region (x, y plane) can beoccupied by charge carriers. The width of the quantum well significantlydetermines the quantum mechanical states that the particles can assumeand leads to the formation of energy levels (sub-bands), i.e. theparticle can only assume discrete (potential) energy values.

“Recombination”

In general, a distinction is made between radiative and non-radiativerecombination. In the latter case, a photon is generated which can leavea component. A non-radiative recombination leads to the generation ofphonons, which heat a component. The ratio of radiative to non-radiativerecombination is a relevant parameter and depends, among other things,on the size of the component. In general, the smaller the component, thesmaller the ratio and non-radiative recombination increases in relationto radiative recombination.

“Refresh Time”

Refresh time is the time after which a cell of a display or similar mustbe rewritten so that it either does not lose the information or therefresh is predetermined by external circumstances.

“Die” or “Light-Emitting Body”

A light-emitting body or also a die is a semiconductor structure whichis separated from a wafer after production on a wafer and which issuitable for generating light after an electrical contact duringoperation. In this context, a die is a semiconductor structure, whichcontains an active layer for light generation. The die is usuallyseparated after contacting, but can also be processed further in theform of arrays.

“Slot Antenna”

A slot antenna is a special type of antenna in which instead ofsurrounding a metallic structure in space with air (as a nonconductor),an interruption of a metallic structure (e.g. a metal plate, awaveguide, etc.) is provided. This interruption causes an emission of anelectromagnetic wave whose wavelength depends on the geometry of theinterruption. The interruption often follows the principle of thedipole, but can theoretically have any other geometry. A slot antennathus comprises a metallic structure with a cavity resonator having alength of the order of magnitude of wavelengths of visible light. Themetallic structure can be located in or surrounded by an insulatingmaterial. Usually, the metallic structure is earthed to set a certainpotential.

“Field of Vision”

Field of view (FOV) refers to the area in the field of view of anoptical device, a sun sensor, the image area of a camera (film orpicking up sensor) or a transparent display within which events orchanges can be perceived and recorded. In particular, a field of view isan area that can be seen by a human being without movement of the eyes.With reference to augmented reality and an apparent object placed infront of the eye, the field of view comprises the area indicated as anumber of degrees of the angle of vision during stable fixation of theeye.

“Subpixels”

A subpixel (approximately “subpixel”) describes the inner structure of apixel. In general, the term subpixel is associated with a higherresolution than can be expected from a single pixel. A pixel can alsoconsist of several smaller subpixels, each of which radiates a singlecolor. The overall color impression of a pixel is created by mixing theindividual subpixels. A subpixel is thus the smallest addressable unitin a display device. A subpixel also comprises a certain size that issmaller than the size of the pixel to which the subpixel is assigned.

“Vertical Light Emitting Diode”

In contrast to the horizontal LED, a vertical LED comprises oneelectrical connection on the front and one on the back of the LED. Oneof the two sides also forms the light emission surface. Vertical LEDsthus comprise contacts that are formed towards two opposite main surfacesides. Accordingly, it is necessary to deposit an electricallyconductive but transparent material so that on the one hand, electricalcontact is ensured and on the other hand, light can pass through.

“Virtual Reality”

Virtual reality, or VR for short, is the representation and simultaneousperception of reality and its physical properties in a real-timecomputer-generated, interactive virtual environment. A virtual realitycan completely replace the real environment of an operator with a fullysimulated environment.

In addition to the structure of a μ-LED and various methods for itsmanufacture, the following aspects of light extraction may be useful forthe realization of the various embodiments and applications concerningaugmented reality described herein and in the PCT applicationPCT/EP2020/052191 incorporated herein by reference.

In one aspect a rear decoupling can be provided. For this purpose, asemiconductor layer stack with a first doped and a second doped layer isprovided, which is arranged on a substrate. The area of the substratefacing away from the layer stack is designed for light extraction. Thelayer stack comprises an active region which is arranged between thefirst doped and the second doped layer. The layer stack is provided witha reflective contact on the surface facing away from the substrate. Thereflective contact extends isolated from the doped layers along a sidesurface to the substrate surface. The shape of this reflective contactis spherical or paraboloidal or ellipsoidal to direct the lightgenerated in the active layer towards the substrate. The substrate iseither very thin or transparent. Further light shaping and/oroutcoupling measures can be provided on the area of the substrate facingaway from the layer stack.

In the previous aspects of improving light extraction, the focus was onthe directionality of the emitted light, among other things. For manyapplications, however, a Lambertian radiation characteristic isrequired. This means that a light-emitting surface ideally has a uniformradiation density over its area, resulting in a vertically circulardistribution of radiant intensity. For a user, this surface then appearsequally bright from different viewing angles. In addition, such auniform distribution can be more easily reshaped by light-shapingelements arranged downstream.

It is therefore proposed that an optical pixel element for generating apixel of a display should comprise of a flat carrier substrate and atleast one μ-LED with rear output. The PLED forms an optical emitterchip. A flat carrier substrate is understood to be, for example, asilicon wafer, semiconductor materials such as LTPS or IGZO, insulationmaterial or similar suitable flat carrier structure, which canaccommodate a large number of μ-LEDs arranged next to each other on itssurface.

The function of such a carrier substrate is, among other things, theaccommodation of functional elements such as ICs, electronics, powersources for the μ-LEDs, electrical contacts, lines and connections, butalso, in particular, the accommodation of the light-emitting μ-LEDs. Thecarrier substrate can be rigid or flexible. Typical dimensions of acarrier substrate can, for example, be 0.5-1.1 mm thick. Polyimidesubstrates with thicknesses in the range of 15 μm are also known.

The at least one μ-LED is arranged on one side of the carrier substrate.In other words, the carrier substrate has two opposite main surfaces,which are referred to here as the assembly side and the display side.The assembly side is the surface of the carrier substrate, often alsoreferred to as the top side, which accommodates the at least one μ-LEDand which may further comprise optical or electrical and mechanicalcomponents or layers.

The display side should describe the side of the carrier substratefacing a user and on which the pixels for display should be perceived.In addition, a carrier substrate plane is described, which extendsparallel to the two main surfaces of the carrier substrate in the sameplane. The at least one μ-LED is configured to emit light transverse tothe carrier substrate plane in a direction away from the carriersubstrate. However, this property should not exclude that lightcomponents are also emitted directly or indirectly in the direction ofthe mounting side of the carrier substrate.

A flat reflector element is provided on the pixel element. This is basedon the idea that a more uniform spatial distribution of the light overthe surface of the pixel element can be achieved by reflection. For thispurpose, the reflector element is spatially arranged on the assemblyside relative to the at least one μ-LED and configured with regard toits shape and composition in such a way that light emitted by the atleast one μ-LED is reflected in the direction of the carrier substrate.

In other words, the reflector element is placed in an area around the atleast one μ-LED through which the emitted light of the μ-LED passes.This reflector element can, according to an example, be a separateprefabricated microelement that is separately applied. Typicaldimensions of such a reflector element can range from 10 μm to 300 μm indiameter, depending on the design variant also in particular between 10μm and 100 μm. According to an aspect, the reflector element isconfigured as a reflective coating or layer of at least one μ-LED.According to an example, the at least one μ-LED can have a transparentor partially transparent coating such as IGZO on its surface, to which areflective layer is then applied.

The reflective layer can, for example, be metallic or contain a metal ina mixture of substances. The aim here is that as much of the lightemitted by the at least one μ-LED as possible is reflected in order toachieve a high yield. The carrier substrate is configured to be at leastpartially transparent so that light reflected by the reflector elementstrikes the surface of the mounting side of the carrier substrate andpropagates through the carrier substrate. This light emerges at leastpartially on the opposite display side of the carrier substrate and canthus be perceived as a pixel by the viewer.

In other words, the emitted light is decoupled at the back or rear ofthe opposite display side of the carrier substrate. The reflectioneffects, refraction effects and, if necessary, damping effects can thusbe used to achieve advantageous more uniform illumination and a morehomogeneous distribution of luminous intensity. According to an example,the reflector element is arranged and configured in such a way that aLambertian radiation characteristic is achieved.

In one aspect, the reflector element has a diffuser layer on its sidefacing the at least one μ-LED. This is intended in particular to scatterthe light reflected by the at least one μ-LED. Alternatively oradditionally, a reflector material comprises diffuser particles. Bydiffusion is meant here that a further scattering or distribution of thelight in a surrounding spatial area should be achieved. This can alsohave a beneficial effect on the scattering or distribution of light andthus achieve a more uniform or homogeneous distribution of the lightintensity, especially on the display side of the carrier substrate.

A diffuser layer can be understood as an additional layer on thereflector element, which can be either uniform throughout, but alsointerrupted or only partially applied. In one aspect, the diffuser layerand/or the diffuser particles have Al₂O₂ and/or TiO₂. These materialscan support a diffusion of the emitted light due to their structuralproperties. While a diffuser layer can only be applied to the surface ofthe reflector, diffuser particles can, for example, be part of a mixtureof materials of the entire reflector and thus be easier to manufacture.

According to an aspect, the reflector element surrounds roundly,polygon-like or parabolically the at least one μ-LED. The underlyingconsideration can be seen in the fact that in many cases the at leastone μ-LED has a spatially wide radiation pattern. This means that lightis emitted in a wide angular range starting from a small area. It isdesirable that as much of this emitted light as possible is captured bythe reflector element and deflected or reflected towards the displayside of the carrier substrate. In this context, it may also be provided,for example, that the at least one μ-LED comprises a first and a secondμ-LED provided for redundancy. This can take over the function of thefirst μ-LED in the event of production-related failure of the firstμ-LED. Control and manufacturing techniques are disclosed in thisnotification. The reflector element, which surrounds both μ-LEDs thusensures uniform radiation regardless of which of the two μ-LEDs isactivated during operation. In another aspect, the reflector elementsurrounds at least three individual μ-LEDs, which emit different colorsduring operation. This means that a reflector element can be providedfor each pixel of a μ-display.

Depending on the radiation pattern of the at least one μ-LED, accordingto an example, arc-shaped, round, dome-like, cap-like or similar shapesof the reflector element are conceivable. The reflector element can,also according to an example, be made in one or more parts or beprovided with recesses or interruptions. According to another example,the reflector element has different reflection properties depending onthe wavelength of the light. This can be achieved, for example, bymicrostructures on the reflector element or its structural composition.

According to an example, the reflector element is configured as a flatsurface which is arranged perpendicular to the carrier substrate planeabove the at least one μ-LED. According to an aspect, the reflectorelement forms an electrical contact of the at least one μ-LED. Theconsideration here is that due to the metallic design of the reflectorelement, for example, a simultaneous use as a connecting contact for theμ-LED can be considered. For this purpose, an electrical contact withone of the μ-LED connections must be provided according to an example.

According to an aspect, the reflector element is configured and shapedin such a way that at least 90% of the light emitted by at least oneμ-LED impinges on the assembly side of the carrier substrate at an angleof 45°-90° relative to the carrier substrate plane. According to anexample, this proportion is at least 95%, according to another exampleat least 80%. The underlying idea is the need for the highest possibleyield. This means that as much of the light emitted by at least oneμ-LED as possible should be emitted on the display side of the carriersubstrate.

One effect that can occur with flat transparent or partially transparentsubstrates is total reflection. This means that light hitting thesurface of the placement side at an acute angle is refracted whenentering the denser medium of the carrier substrate. As a result, thelight is reflected multiple times within the carrier substrate betweenthe placement side and the display side and does not exit the carriersubstrate because of the too acute angles to the interfaces. Theseproportions are usually to be considered as losses. In order to avoidthese losses, it may be desirable for the light to strike the surface ofthe placement side of the carrier substrate at the greatest possibleangle, ideally perpendicularly. Accordingly, the reflector element isconfigured to create these angular relationships and in particular toreduce crosstalk between the pixel elements. In one aspect, the carriersubstrate comprises polyimide or glass. Polyimide is a material that canbe used especially for flexible displays. Glass can serve as amechanically very stable base material for rigid displays.

According to an aspect, a passivation layer is additionally provided toattenuate or eliminate reflections at mesa edges of the at least oneμ-LED. A mesa edge is defined as a wall or contour that generally slopessteeply to form the boundary of the at least one μ-LED. This is arrangedwith its surface transverse to the carrier substrate plane. To avoidcrosstalk, it is desirable that no light passes over in the direction ofthe respective adjacent pixel element. For this purpose, lightcomponents that emerge in this direction should be eliminated or atleast attenuated by an appropriate damping layer or passivation layer.The advantage here can be better contrast and reduction of opticalcrosstalk.

According to an aspect, a light-absorbing coating is provided on theassembly side and/or the display side of the carrier substrate outsidethe reflector element. It can be considered desirable that thenon-active areas between the μ-LEDs, especially between differentpixels, are opaque or attenuate light in order to improve contrast anddarker impression. The light-absorbing coating is therefore placedoutside the reflector element. According to an aspect, the display sideof the carrier substrate has a roughened or uneven and/or roughenedstructure. This structure is such that it causes scattering or diffusioneffects for the wavelength of the relevant light spectrum. This can havethe advantage, for example, that a higher proportion of the lighttransmitted through the carrier substrate can be coupled out at thedisplay side. Due to the rough structure, more favorable microstructuralangular relationships are created, which can allow more effectivedecoupling.

According to an aspect, a color filter element is arranged on thedisplay side of the carrier substrate opposite the reflector element.This color filter element allows a primary color spectrum of the leastone μ-LED to pass and attenuates other color spectra. An advantage canbe a better color rendering and better contrasts by eliminating lightportions of adjacent pixel elements with different colors.

Furthermore, a process for the production of an optical pixel element isproposed. In a first step, at least one μ-LED is attached to a mountingside of a flat carrier substrate. Then a reflector element is produced,for example as a reflective layer of the at least one μ-LED. Accordingto an example, before attaching the at least one μ-LED to the carriersubstrate, a display side of the carrier substrate is processed formicro-structuring and/or roughening. An advantage can be seen in thefact that the respective surfaces can be finished before the moresensitive electronic and optical components are applied to the assemblyside.

A substantial aspect of light extraction is the ability to suppressunwanted light components. In some applications, a highly directionallight is also desired. The μ-LED or pixel should therefore not have aLambertian characteristic but a high directionality. In some cases, onthe other hand, an unconverted portion of the converted light should beblocked or at least deflected in such a way that it does not reduce thevisual impression.

Some of these properties can be achieved by providing a photonicstructure or photonic crystal on the exit side of the light. In thefollowing, some aspects are described, which illustrate differentmeasures to collimate generated light to reduce the emission angle orotherwise shape it. Besides micro lenses or other measures, theseinclude photonic structures. These change the emission behaviour bycreating a “prohibited” area where light emission is not allowed.Accordingly, light emission in one or more directions can be suppressedor promoted.

In some aspects, an optoelectronic device may have a stack of layerswith an active region for generating electromagnetic radiation. Thedevice comprises at least one further layer having a photonic crystalstructure. At least some of the layers of the layer stack aresemiconductor layers. The stack of layers may include a p-doped layerand an n-doped layer, as well as a p-doped and an n-doped GalliumNitride (GaN) layer forming the active region between the two layers. Itshould be noted that the layer stack forms a μ-LED, which may have oneor more features of this disclosure in terms of geometry, materialsystem, structure or processing.

At least one layer on the stack of layers can have a photonic crystalstructure, especially a 2-dimensional structure. The photonic crystalstructure can be arranged at least in a portion of the layer and can beformed for example by wire-like or cylindrical structures having alongitudinal direction which is at least substantially parallel to thegrowth direction of the layer. The structure forming the photoniccrystal, such as the wires or cylinders, may comprise a first material,for example the material of the layer, while the space between thestructure may be made of or filled with a second material having adifferent refractive index than the first material. The second materialcan be air or another substance, for example a conversion material.

The photonic crystal structure can be used to manipulate light generatedin the active region as the light passes through the photonic crystalstructure. In particular, the photonic crystal structure can be arrangedso that light passing along the direction of growth can pass through thephotonic crystal structure, while light passing at an angle close to orat 90 degrees with respect to the direction of growth cannot passthrough the photonic crystal structure. This is particularly the casefor light having wavelengths, which are within a photonic band gapformed by the photonic crystal structure.

In some aspects, the periodicity is at about half of a specificwavelength. This is the wavelength corresponding to the wavelength ofelectromagnetic radiation that must be diffracted by the photoniccrystal structure. Thus, a periodicity in the range of 350 nm to 650 nmis appropriate for operation in the visible region of the spectrum—oreven less, depending on the average refractive index. The repeatingranges of different dielectric constants in the photonic crystalstructure can therefore be produced in this order of magnitude. In someaspects, an integer multiple of the corresponding wavelength can also beused.

In some embodiments, the layer with the photonic crystal structure is adielectric layer, which contains or consists of silicon dioxide, SiO₂,for example. This can be an additional layer, which is added to theusual layers of a μ-LED. The same fabrication technology can thereforebe used for GaN and GaP systems. The different manufacturing variantsand possibilities can also be transferred to a converter layer. Thus, agreater bundling or collimation can be achieved compared to standardLEDs without such a structure. Also, the extraction efficiency with aphotonic crystal structure applied in one layer is improved compared toa conventional LED without a photonic crystal structure.

In some aspects, the optoelectronic device may comprise one or moremirror layers arranged on top of the layer with the photonic crystalstructure. The mirror layer or layers may be arranged to form anangle-selective mirror, for example as a cover layer. The concentrationof the emitted light can be further improved. With beam-shapingstructures, as given by using a layer with a photonic crystal structure,up to 50% more light can be emitted into a 30 cone or less on the chipplane compared to a standard chip having a roughened surface. Such beamshaping allows high efficiency and low cost in projection applications.For μ-LED or monolithic display applications it may even be arequirement.

The different photonic decoupling structures create a certain roughnessand surface structures on the surface, depending on their design. Inaddition, light emitting diodes often have a structured surface in thepast to improve light outcoupling. In contrast, the stamping technologycurrently used to place μ-LEDs on electrical contacts is only possiblefor μ-LEDs with planar or flat surfaces.

Therefore a method of making photonic structures on a μ-LED, in which anoptical outcoupling structure is created in a surface region of asemiconductor body providing the μ-LED. The surface area with theoutcoupling structure is then further processed and planarized. In thisway, a planar surface is obtained, but light shaping and outcoupling isstill improved by means of the outcoupling structure.

Accordingly, a μ-LED thus contains a decoupling structure, which isarranged in a planar surface area. The output structure can also havelight-shaping features, such as the photonic structures revealed here.This allows light to be emitted from a surface perpendicular to it.

In one aspect, the surface region of the semiconductor body isstructured by generating a random topology at the surface region. Arandom topology involves directly roughening the surface of the surfaceregion. Alternatively, a transparent second material, especially Nb₂O₅with a high refractive index can be applied and then roughened.

In another aspect, the surface area is structured by an ordered topologyand then planarized according to the explanations revealed here. Forthis purpose, photonic crystals or non-periodic photonic structures,especially quasi-periodic or deterministic aperiodic photonicstructures, are introduced into a second transparent material.Interstitial spaces are filled and then planarized. Filling is done witha transparent third material with a low refractive index, especiallysmaller than 1.5, especially SiO₂.

The planarization is done by mechanical or chemical-mechanical polishing(CMP). This creates a planarized surface with a roughness in the rangeof less than 20 nanometers, in particular less than 1 nanometer, as themean roughness value.

As already mentioned, a photonic crystal or other structure can beapplied to the μ-LED or μ-LED array to form the beam of an LED or μ-LED.However, in some applications it is common to use non μ-LEDs that emitlight of different wavelengths in one operation. Instead, one type ofμ-LED is used and its emitted light is then converted. For this purpose,a converter material is applied to the surface of the μ-LED in the mainradiation direction. The photonic crystal as light-shaping structure isarranged above the converter material as already revealed in someexamples.

In the following, further aspects are explained, which are based on theidea of unification of light shaping and converting structure so that aparticularly space-saving arrangement of the individual elements andthus a particularly small design of an optoelectronic component ispossible. This achieves that the radiation emitted by the component isspecifically radiated into a certain area of space, while radiation intoother areas is reliably prevented in a comparatively simple way. Inaddition, all solutions with photonic structures presented here arecharacterized by high energy efficiency and thus by a comparatively goodlight yield compared to the known technical solutions.

In this context, some aspects first concern a converter element for aμ-LED. The converter element comprises at least one layer with aconverter material which, when excited by an incident excitationradiation, emits a converted radiation into an emission area. Theconverter element is characterized in that the layer has a photonicstructure at least in some areas, on which the converter material isarranged at least in sections. The photonic structure is designed insuch a way that the radiation is emitted as a directed beam of rays intothe emission area. Thus, a layer is provided which is structured in asuitable manner, wherein a converter material is applied in or on thestructure, which emits converted radiation when excited by an excitationor pump radiation.

By combining the components converter material on the one hand andstructured layer for targeted beam guidance and/or shaping on the otherhand, an element is created in a particularly space-saving manner whichenables a targeted emission of radiation into the radiation source'sradiation area, limited to a desired spatial area. In this context, itis conceivable that both the converted radiation emitted by theconverter element and the excitation radiation are directed in asuitable manner so that radiation is only emitted in a certaindirection, while the emission of such radiation in other directionsand/or areas is excluded or at least significantly reduced.

In general, it is conceivable that the photonic structure is coated witha suitable converter material at least in some areas and/or at leastindividual areas, for example depressions in the structure, are filledwith the suitable converter material. The structure is configured insuch a way that the emitted converted radiation is emitted as a beam ofrays in a desired direction of the radiation area. Thus, light is bothconverted and shaped by the photonic structure. In this context, it isconceivable to adapt the photonic structure in a suitable way so thatdifferent areas are present into which a beam of radiation is emitted.In this way, converter elements can be provided which adjust theradiation characteristics of an optoelectronic component or a μ-LED inwhich they are used as required. In particular, it is possible toprovide a converter element by which the emission profile of anoptoelectronic component for which the converter element is used can bechanged in such a way that the radiation no longer follows Lambert'slaw, but instead a beam or bundle of rays is generated which is directedin a specific direction.

The converter material may include the materials disclosed in thisapplication and may be doped with various rare earth elements. As hostmaterial the already mentioned YAG or LuAG can be used. It is alsopossible to use the already mentioned quantum dots as convertermaterial. The photonic structure normally does not change the spectralproperties of a quantum dot. Besides the adaptation of the photonicstructure to the emission spectrum of the quantum dots, they can also belocated in the area of the structure itself, e.g. in formed trenches

The regular photonic structure or a regular photonic crystal offers theadvantage that the optical properties of the converter element can beadjusted particularly reliably, safely and reproducibly with anappropriate structured layer. The structure is configured in such a waythat radiation of a certain wavelength or a certain wavelength range canpenetrate the layer in a specifically defined direction, while thisradiation cannot penetrate the layer in other directions. Alternativelyor additionally, the structured layer can be configured in such a waythat it is transparent or non-transparent for radiation of a specificwavelength over at least a large range.

Furthermore, it is useful if the photonic structure has at least onerecess in which the converter material is located. Preferably, in thiscontext it is intended that the photonic structure has a plurality ofelevations and depressions, the depressions being at least partiallyfilled with the suitable converter material. In this way, a converterelement can be realized comparatively easily, in which the structureprovided according to the invention is combined with the convertermaterial in such a way that the converted radiation is emitted only in aspecifically limited radiation range and thus in a particularly targetedmanner. In principle, it is conceivable in this regard that theconverter element is configured in such a way that the excitationradiation is directed by the photonic structure in a targeted manneronto areas of the converter material provided for this purpose and/orthat the converted radiation impinges on the structure and is thusemitted as a targeted beam of radiation into the desired radiationemission range.

In some aspects, the layer with the photonic structure is configuredsuch that the layer comprises at least one optical band gap. In thiscontext, a band gap is understood to be the energetic range of the layerthat lies between the valence band and the conduction band. Due to theband gap, the solid used for the layer and thus the converter elementprovided with the layer are transparent to radiation in a certainfrequency range. The optical properties of the converter element can bespecifically adjusted by adjusting the band gap and/or selecting a solidstate material. In particular, it is possible to adapt the layer in sucha way that only a part of the incident radiation passes through thelayer and is emitted into the emission range. In some aspects, it isuseful if the photonic structure of the layer has an average thicknessof at least 500 nm, so that an optical band gap is created.

In some embodiments, it is provided that the layer with the photonicstructure is configured in such a way that the directed beam of rays isemitted perpendicular to a plane in which the layer is arranged. Incontrast, radiation components that are emitted into other spatial areasare reliably suppressed.

Further aspects concern optical filter elements and other measures. Inone aspect, an optical filter element can be arranged at least on oneside of the layer. In some aspects, such a filter element is designed asa filter layer, which is applied flat on the structured layer with theconverter material. With the aid of such a filter element or such afilter layer, it is possible that only a certain part of a radiationimpinges on the layer with the converter material or that only a certainpart of the converted radiation emitted by the structured layer with theconverter material is emitted into the desired spatial region. Thefilter element, in particular the filter layer, is thus adapted in someaspects in such a way that only that part of a radiation can passthrough the filter element or the filter layer which is required asexcitation radiation or which is to be emitted specifically into theemission range.

Furthermore, some aspects concern a radiation source with a μ-LED, whichradiates an excitation radiation into a converter element, which isconfigured according to at least one of the previously describedembodiments of a converter element. The converter element in turn has atleast one layer with a converter material which, when excited by theexcitation radiation emitted by the μ-LED, is excited to emit aconverted radiation into a radiation emission area. In this context itis conceivable that a μ-LED is combined with a converter element in sucha way that the entire excitation radiation emitted by the LED isconverted into converted radiation or that only a part of the excitationradiation emitted by the LED is converted into converted radiation.Again, it is substantial that the radiation emitted into the radiationsource's beam area is only directed into a desired spatial region. Theradiation source thus generates a directed beam of light or a directedbeam of radiation that is emitted in a specifically selected directionor in a specifically selected radiation range.

According to another aspect, the structured layer with the convertermaterial is part of a semiconductor substrate of the μ-LED. The photonicstructure can be formed accordingly in a semiconductor substrate of theμ-LED. In this context, it is also conceivable that the structure isproduced by targeted etching of the LED semiconductor substrate and thestructure is then at least partially coated with converter materialand/or the converter material is filled into etched-out depressions inthe structure.

Furthermore, in some aspects it is planned that the structure with theconverter material is configured in such a way that the convertedradiation is emitted perpendicular to a plane in which the semiconductorsubstrate is located, into the emission area. The structure isconfigured in such a way that converted radiation is only emittedperpendicular to the surface of the μ-LED chip into the emission areadue to a bandgap effect. Due to this technical solution, a highdirectionality of the converted radiation emitted by the converterelement is achieved. In this context, it is also possible that thephotonic structure, for example in the form of a photonic crystal, isarranged only in the uppermost layer of the semiconductor material ofthe μ-LED or also at least partially in the active zone. It is againadvantageous if the photonic structure has a layer thickness of at least500 nm in order to generate reliably an optical band gap.

In one embodiment at least one filter layer is provided, which isarranged on one side of the structured layer. By means of a filterlayer, the excitation radiation generated by the μ-LED is suppressed incertain wavelength ranges. In this way, especially etendue-limitedsystems based on full conversion of the excitation radiation can be madesignificantly more efficient than known technical solutions by means ofdirected radiation generation in the structured layer of the converterelement.

The radiation source may be configured to emit visible white light orvisible converted light with the colors characteristic of the RGB colorspace, namely red, green and blue. According to one embodiment, theradiation source can be a pixelated array, in which, for example,individual pixels of a larger component can be switched on and offindividually.

The use of a photonic structure, as described herein, in combinationwith the above-mentioned μ-LEDs makes it possible to do without lensesor similar collimating elements. Furthermore, a photonic structure canimprove the contrast between adjacent pixels due to the provideddirectionality.

In addition, some aspects also concern a process for manufacturing aradiation source that has at least one of the special propertiesdescribed above. The process is characterized by the fact that thestructure is formed by at least one etching step in a semiconductorsubstrate of the LED. It is advantageous here if the structure, inparticular specifically selected recesses in the structure, are at leastpartially filled with the converter material.

Some further aspects deal with a μ-display with a photonic structure forthe emission of directed light. Especially in displays that featureμ-LEDs, the dimensions of individual μ-LEDs can be very small, so thatwhen a photonic structure is formed, only a few periods have space onthe surface of a single μ-LED. It is therefore proposed to form aphotonic structure over a large area on an array of several μ-LEDs. Sucharrays can be pixelated arrays of μ-LEDs, for example, where one pixelforms a light source. Monolithic pixel arrays also fall under thiscategory as do assembled LED modules with a smooth surface, for examplethe cover electrode disclosed in this application. Another example is anarrangement of single μ-LEDs or smaller modules of μ-LEDs, which canalso be provided in the form of an array. Such μ-LED modules are alsodisclosed in this application.

μ-LEDs are normally Lambertian emitters and therefore emit light in alarge solid angle. For pixelated arrays, and especially for μ-displays,however, as already explained, a directed emission perpendicular to thelight emission surface is important or desirable for a variety ofapplications.

Thus, an optoelectronic device comprises an assembly having a pluralityof light sources for generating light emerging from a light exit surfacefrom the optoelectronic device, and at least one photonic structuredisposed between the light exit surface and the plurality of lightsources. By means of the at least one photonic structure, which may bein particular a photonic crystal or pillar structures, also referred toherein as columnar structures, beam shaping of the emitted light iseffected before the light leaves the device through the light exitsurface.

The photonic structure may be configured in particular for beam shapingof the light generated by the light sources. The photonic structure canin particular be configured in such a way that the light emerges atleast substantially perpendicularly from the light exit surface. Thedirectionality of the emitted light is thus considerably improved.

According to one embodiment, the arrangement is an array comprising aplurality of light sources, in particular μ-LEDs, arranged in rows andcolumns. The μ-LEDs are organized in pixels or subpixels and can becontrolled separately. In some aspects, the arrangement is realized as amonolithic array, in other aspects, the arrangement is equipped withμ-LED modules or separate μ-LEDs. The array comprises one containing orcontacting the μ-LEDs or light sources at least partially and onephotonic crystal. This is arranged or formed in the layer. The photoniccrystal can thus be arranged directly in the layer in which the pixelsof the array are arranged. Alternatively, the photonic crystal isarranged in the layer above the light sources, so that the photoniccrystal is still located between the light sources and the light exitsurface.

The layer may comprise a semiconductor material and the photonic crystalmay be structured in the semiconductor material. Examples ofsemiconductor materials are GaN or AlInGaP material systems. Examples ofother possible material systems are AlN, GaP and InGaAs.

The photonic crystal can be realised by forming a periodic variation ofthe optical refractive index in the semiconductor material, using amaterial with a high refractive index, such as Nb₂O₅ (niobium (V)oxide), and introducing it into the semiconductor material accordinglyto form a periodic or deterministically aperiodic structure. Thephotonic structures can be filled with a material of low refractiveindex, such as SiO₂.

Thus, a refractive index variation between a high and a low indexoccurs. The photonic crystal is preferably formed as a two-dimensionalphotonic crystal, which exhibits a periodic variation of the opticalrefractive index in a plane parallel to the light exit direction in twomutually perpendicular spatial directions.

The photonic crystal can be realized by means of holes or recesses,which are inserted into a material with a high refractive index, forexample Nb₂O₅. The photonic crystal can thus be formed or be formed byforming the corresponding structuring in the material with highrefractive index. In contrast, the material surrounding the holes orrecesses has a different refractive index.

In a further aspect, the arrangement comprises a plurality of μ-LEDs aslight sources, the μ-LEDs being arranged in a first layer and a photoniccrystal being arranged or formed in a further, second layer. The secondlayer is located between the first layer and the light emitting surface.In combination with a particularly array-like arrangement of μ-LEDs, aphotonic crystal can be provided in an additional, second layer abovethe first layer comprising the μ-LEDs. This is preferably designed as atwo-dimensional photonic crystal and is realized in the form of aperiodic variation of the optical refractive index in two spatialdirections running parallel to the light exit surface and perpendicularto one another. As an example of a material with a high refractive indexof the second layer, Nb₂O₅ can again be mentioned here, and the photoniccrystal can be structured by means of holes or recesses in the materialwith the high refractive index. The photonic structures can be filledwith a material with a lower refractive index, for example SiO₂. Thus,the second layer has a structure of a material with two differentrefractive indices.

μ-LEDs can be differentiated between horizontal and vertical μ-LEDs.With horizontal LEDs, the electrical connections are located on the backof the LED facing away from the light emission surface. In contrast, inthe case of a vertical LED, one electrical connection is located on thefront and one on the back of the LED. The front side faces the lightemission surface.

In pixelated arrays, where the electrical contacts of both polaritiesare on the backside, the whole array surface can be structured, e.g. inform of a photonic crystal, especially without leaving mesa trenches orcontact areas. A similar arrangement results for arrangements ofhorizontal μ-LEDs under a carrier substrate. According to an embodiment,in an array or an arrangement of horizontal μ-LEDs for the electricalcontacting of the light sources, both poles can be electricallyconnected in each case by means of a contacting layer reflecting thegenerated light, the contacting layer lying under the photonic structureand the light sources, viewed from an upper light exit surface. Thecontacting layer can thereby have at least two electrically separatedareas in order to avoid a short circuit between the poles.

According to another configuration, in the case of an arrangement ofvertical light emitting diodes for the electrical contacting of thelight sources, a first connecting contact facing away from thelight-emitting surface, in particular a positive one, can beelectrically connected to a contacting layer reflecting the generatedlight, the contacting layer lying below the photonic structure and thelight sources as seen from an upper light-emitting surface. On the otherhand, the respective other, in particular negative, second connectingcontact, which faces the light exit surface, can be electricallyconnected by means of a layer of an electrically conductive andoptically transparent material, in particular ITO. A filling materialcan be arranged between the layer and the reflective contacting layer.In some aspects, this electrically conductive layer may itself bestructured to produce photonic properties. In other aspects, thephotonic structure is created over the electrically conductive layer.

According to an embodiment, each of the light sources or the μ-LEDs canhave a recombination zone and the photonic crystal can be located soclose to the recombination zones that the photonic structure changes anoptical state density present in the region of the recombination zones,in particular in such a way that a band gap is generated for at leastone optical mode with a direction of propagation parallel and/or at asmall angle to the light exit surface.

To effect the optical band gap in the recombination zone, it is usefulif the photonic crystal is very close to the recombination zone. Inaddition, to form the band gap, it is useful if the height of thephotonic crystal is large when viewed in a direction perpendicular tothe light-emitting surface, in particular equal to or above 300 nm. Bymeans of the photonic structure, directionality can thus be achieved forthe emitted light already in the light generation region, since theemission of light with a direction of propagation parallel and/or at asmall angle to the light exit surface can be suppressed. Light can thenonly be generated in a limited emission cone perpendicular to the lightexit surface. The aperture angle of the emission cone depends on thephotonic crystal and can be a small value, for example, maximum 20°,maximum 15°, maximum 10° or maximum 5°.

The photonic crystal can be arranged in relation to a plane parallel tothe light-emitting surface independently of the positioning of the lightpoints.

The photonic structure may comprise a plurality of pillar structuresextending at least partially between the light-emitting surface and theplurality of light sources, one pillar being associated with each lightsource and aligned with the light-emitting surface when viewed in adirection perpendicular to the light-emitting surface. The pillars orcolumns have a longitudinal axis, which preferably extends perpendicularto the light-emitting surface. When a pillar and an associated lightsource are aligned, the extended longitudinal axis of the pillarintersects the centre of the light source.

Viewed transversely to the longitudinal axis, the pillars can have acircular, square or polygonal cross-section. Pillars preferably have anaspect ratio height to diameter of at least 3:1, with the heightmeasured in the direction of the longitudinal axis of the pillars. Inparticular, pillars are made of a material with a high refractive index,such as Nb₂O₅. Due to the higher refractive index compared to thesurrounding material, the light emission in a direction parallel to thelongitudinal axis of the pillars can be increased compared to otherspatial directions. The pillars act as wave guides. Light is moreefficiently coupled out along the longitudinal axis of the pillars thanalong other propagation directions. Directionality in the direction ofthe longitudinal axis of light can thus be improved. Since thelongitudinal axis of the light is preferably perpendicular to the lightexit surface, improved light extraction perpendicular to the light exitsurface can also be achieved.

The arrangement may be an array comprising as light sources a pluralityof μ-LEDs arranged in pixels arranged in a first layer and the pillarsmay be arranged in a further, second layer, the second layer beingpositioned between the first layer and the light emitting surface. Thus,the pillars can be arranged on the surface of the pixelated array. Thepillar or column structures can be free-standing and made of a materialwith a high refractive index. In addition, the free space between thepillars can be filled with a filling material, e.g. SiO₂, with a lowrefractive index.

In another aspect, the arrangement can be an array that has as lightsources a plurality of pixels arranged in a first layer, and the pillarscan also be arranged in the first layer. In particular, the pillars maybe arranged in the first layer such that at least a respective part of apillar is closer to the light emitting surface than the light sourceassociated with the pillar. The pillar can thus act as an opticalwaveguide between the light source and the light-emitting surface. Thepillars can be formed from a semiconductor material of the arrayprovided in the first layer, the semiconductor material having a highrefractive index. In particular, semiconductor material in the firstlayer can be removed by etching in such a way that the pillars remainstationary. The free spaces between the pillars can in turn be filledwith a low refractive material.

In a further aspect, the arrangement can be an array that has as lightsources a plurality of μ-LEDs arranged in pixels, with the pixels beingformed in the pillars. An array can thus be created in such a way thatthe individual pixels have the form of pillars. Each pillar ispreferably a μ-LED and functions as a single pixel. Seen in relation tothe longitudinal axis of a pillar, the length of the pillar cancorrespond to half a wavelength of the emitted light, and therecombination zone of the μ-LED formed by a pillar is preferably locatedin the centre of the pillar. Thus, the recombination zone lies in alocal maximum of the photonic state density. The light emission parallelto the longitudinal direction of the pillars can thus be significantlyincreased. Due to the waveguide effect, the light with propagationdirection parallel to the longitudinal axis is additionally coupled outmore effectively than light of other propagation directions.

The aspect ratio of height to diameter of a pillar is preferably 3:1,and at common emission wavelengths, the pillars have a height of about100 nm and a diameter of 30 nm. Also up-scaled, larger heights anddiameters, respectively are possible, which are easier to manufacture.In such a case, it is useful if the aspect ratio remains the same, forexample the 3:1 mentioned above, but in a fixed ratio to the wavelengthof the light to be influenced. The space between the pillars containingthe light sources can be filled with material, for example SiO₂, whichhas a lower refractive index than the semiconductor material for thepillars.

In the case of a pillar with a light source, a p-contact can be made onthe underside of the pillar facing away from the light-emitting surface.For example, an n-contact can be made at half the height of the pillarson the top of the pillar. The n-contact can be produced by a transparentconductive material, especially as an intermediate layer in the fillingmaterial or as the top layer above the pillars. A possible material foran n-contact layer is for example ITO (indium tin oxide). An inversearrangement of n- and p-contact is also possible.

In particular, in the case of an arrangement of light emitting diodes,in particular vertical light emitting diodes in the form of pillars orcolumns for electrical contacting, a respective first pole, inparticular a positive pole, may be electrically connected to areflective contacting layer which may be formed on and/or along firstlongitudinal ends of the light emitting diodes. The respective other, inparticular negative, second pole can be electrically connected to afurther layer of an electrically conductive and optically transparentmaterial, in particular ITO. This layer can be arranged as anintermediate layer in the middle of the pillars or columns or at and/oralong second longitudinal ends of the pillars, the second longitudinalends being opposite the first longitudinal ends.

According to another aspect, an optoelectronic device is proposed forgenerating an emission of light directed perpendicularly to an emittingsurface from an, in particular planar, pixel array or from an array ofμ-LEDs, whereby optically acting structures, in particularnanostructures such as a photonic crystal or a pillar structure, arestructured along the entire emitting surface to the perpendicularlydirected emission of the light. According to a further aspect, a methodis proposed for the manufacture of an optoelectronic device forgenerating an emission of light directed perpendicularly to an emittingsurface from an, in particular planar, pixelated array or from an arrayof μ-LEDs, wherein optically acting structures are structured along theentire emitting surface to the perpendicularly directed emission of thelight.

Planar array means in particular plane array. A surface of an array orfield is also preferably smooth. A pixelated array is especially amonolithic, pixelated array.

All mentioned materials, especially the materials in a photonic crystal,a pillar, or the filling materials preferably have a low absorptioncoefficient. The absorption coefficient is here in particular a measureof the reduction in the intensity of electromagnetic radiation whenpassing through a given material.

The photonic crystal can be produced using a lithography technique knownper se. Possible technologies known per se are, for example, nanoimprintlithography or immersion EUV stepper, where EUV stands for extremeultraviolet radiation.

Another possible application of photonic crystals is based on theproperty of polarizing electromagnetic radiation, especially visiblelight, with respect to the direction of oscillation. With the help ofphotonic structures for polarization of electromagnetic radiation, it isespecially possible to take special pictures and show them on suitabledisplays. To create images, which give the impression of athree-dimensional image to a user, usually several complementarypolarization, directions are combined in a suitable way.

It is therefore regularly a problem that the lighting units, which canprovide polarized light on demand, comprise a number of additionaloptical components in addition to the emitter used to generate light.This makes the construction of corresponding lighting unitscomparatively complex and increases the costs of production.Furthermore, the different components require a not inconsiderableamount of installation space, so that efforts to miniaturize thelighting units required for augmented reality applications or in thefield of consumer electronics, often reach their limits. More recentrequirements in the automotive sector also point to the desire to createimages that create a three-dimensional effect on the user.

To solve this and other problems, an arrangement or an optoelectroniccomponent is proposed with at least one emitter unit, in particular aμ-LED, which emits radiation via a light exit surface. The componentalso comprises a polarization element, which is connected at least insections to the light-emitting surface and changes a polarization and/oran intensity of the radiation emitted by the emitter unit when theradiation passes through the polarization element. The arrangement ischaracterized in that the polarizing element comprises athree-dimensional photonic structure.

The device or optoelectronic component can be a pixel element of aμ-display or a μ-display module. The emitter unit can be formed by aμ-LED. One or more such modules, in which several pixels are arranged inrows and columns, can thus generate one or more images, which may givethe user the impression of a three-dimensional image.

The formulation that the polarizing element changes a polarization alsoincludes the generation of polarized radiation from non-polarizedradiation. The polarizing element can also only change the intensity ofthe radiation, possibly depending on the wavelength, without producingor changing a polarization. The term “polarizing element” is thereforenot to be interpreted narrowly in the sense that a change or generationof polarization must be provided for in all configurations.

The proposed solution provides an optoelectronic component in which theradiation generated by the emitter, for example a μ-LED, passes directlyinto the polarizing element, so that a particularly compact unit forproviding demand-polarized radiation is realized, which in turn can becombined with further such components and/or a polarizing element,preferably with at least one polarizing element that has complementaryproperties.

The substantial advantage of using a three-dimensional photonicstructure, in particular a photonic crystal, for polarizingelectromagnetic radiation, whereby preferably visible light ispolarized, is that a particularly compact, space-saving solution isprovided by the arrangement of the photonic structure in the area of thelight exit surface of the emitter. With the aid of the speciallyconfigured polarizing element adjacent to the light-emitting surface, itis possible to polarize electromagnetic radiation in a targeted mannerand still minimize the losses of radiation whose polarization does notcorrespond to the polarization direction of the polarizing element. Ingeneral, it is conceivable that the photonic structure is arranged onthe light-emitting surface, or that a photonic structure is formed in asuitable manner in a semiconductor layer on which the light-emittingsurface is located or to which the light-emitting surface is adjacent inthe direction of the beam.

Here it is of particular advantage that the three-dimensional structuresused as polarization elements can be used to change the radiationcharacteristics of an illumination unit with regard to its polarizationproperties in a particularly effective way, thus enabling discriminationof different wavelengths by different polarization properties orradiation directions.

According to an aspect, the emitter unit has at least one μ-LED. In thiscontext, it is conceivable that the μ-LED emits preferably white, red,green or blue light, which is irradiated into the polarizing element andby means of the polarizing element the radiation is polarized in anoscillation direction. In this context, the μ-LED may also comprise aconverter material so that the light emitted by the μ-LED is convertedby the converter material into a desired wavelength and thus color.

Furthermore, according to another aspect, the emitter unit, inparticular a μ-LED, as well as the polarization element are to be formedfrom different layers, which are arranged in a layer stack one above theother. Again, it is substantial that the radiation generated in at leastone layer of the emitter reaches the likewise layer-shaped polarizingelement before the radiation from the layer stack is emitted into theenvironment. In this context, it is advantageous that thethree-dimensional structure used as a polarization element is located onor in the same semiconductor chip as the emitter unit.

When using an emitter unit with a μ-LED, it is also conceivable that thephotonic structure is applied to the μ-LED chip or at least is part ofthe μ-LED chip. Various designs of such a μ-LED are disclosed in thisapplication. The μ-LED may be monolithically manufactured and may bepart of a larger array of μ-LEDs arranged in rows and columns. These canbe processed and manufactured together. The μ-LEDs for individual colorscan be combined into a pixel and surrounded with a structure to improvelight guidance, especially to the main beam direction.

Such an embodiment provides a particularly space-saving andenergy-efficient optoelectronic component with which polarized radiationis already generated directly at chip level without the need foradditional optical elements in the downstream beam path.

In other aspects, the polarization element has spiral and/or rod-shapedstructural elements. In this case, the three-dimensional photonicstructure is adapted in such a way that light emitted by the emitterunit or the μ-LED only leaves the photonic structure with a certainpolarization. A corresponding three-dimensional photonic structure withspiral and/or rod-shaped structural elements in the area of the lightexit surface is only irradiated by radiation with a specificpolarization direction. The design and dimensioning of the structure ispreferably adapted to the radiation emitted by the emitter unit. Aspiral structure achieves a circular polarization, while a rod-shapedstructure causes a linear polarization of the radiation passing throughthe structure.

According to further aspects, it is also conceivable that when using aconverter material, the three-dimensional photonic structure is locatedin the beam path between the μ-LED and the converter element or behindthe converter element, by which the excitation radiation and/or theconverted radiation is polarized in a suitable way. The combination ofconverter element and three-dimensional photonic structure in the samelayer can also be realized. Thus, directly polarized, converted lightcan be generated.

For example, converter material can be filled into the three-dimensionalphotonic structure. The converter material can be doped with Ce³⁺ (Cefor cerium), Eu²⁺ (Eu for europium), Mn⁴⁺ (Mn for manganese) orneodymium ions. As host material, for example YAG or LuAG can be used.YAG stands for Yttrium-Aluminium-Garnet. LuAG stands for lutetiumaluminum garnet.

Quantum dots can also be filled into the three-dimensional photonicstructure as converter material. Quantum dots can be very small, forexample in the range of 10 nm. They are therefore particularly suitablefor filling the three-dimensional photonic structure. In general, it isconceivable that the structure is produced by etching material out ofthe layer, in which the structure is to be formed. The recesses thusformed can then be filled with converter material containing, forexample, quantum dots. The quantum dots can, for example, be introducedinto a liquid material with which the recesses are filled. The liquidmaterial can be at least partially vaporized so that the quantum dotsremain in the recesses. In the process, part of the liquid material cansolidify. The quantum dots can therefore be embedded in a matrix.

The photonic structure normally does not change the spectral propertiesof a quantum dot. However, a quantum dot has a narrowband emissionspectrum. The photonic structure can be adapted to this narrowbandemission spectrum, which can improve the directional selectivity causedby the photonic structure.

By means of a photonic structure, the radiation characteristics ofquantum dots can thus be influenced very efficiently as converters.

In other aspects, the polarizing element has at least onethree-dimensional photonic crystal. It is also conceivable that thepolarizing element comprises at least two two-dimensional photoniccrystals, which are arranged one behind the other along a beam path ofthe radiation penetrating the polarizing element.

It is useful to use one three-dimensional photonic crystal or at leasttwo two-dimensional photonic crystals arranged one behind the other inthe optical path so that the structure on which the radiation impingesis transparent to radiation of a specific wavelength or several specificwavelengths and/or only transmits it in a specific direction. In thisway, the desired polarization of the radiation impinging on thepolarizing element can also be adjusted. In this context, it isconceivable to produce the structure directly in the converter materialor to insert it into an additional layer of another material. Theproperty of the three-dimensional photonic structure is preferablydesigned such that the transmission conditions are different fordifferent wavelengths. In this way it is possible, for example, thatconverted radiation can pass the polarizing element unhindered while theexcitation radiation is deflected. It is also conceivable that at leastone of the radiations, namely excitation radiation on the one hand andconverted radiation on the other hand, only passes through thepolarizing element with a certain polarization.

In some embodiments, it may also be provided that the polarizing elementhas at least two different transmittances depending on a wavelength ofthe radiation passing through the polarizing element. In this context, afurther embodiment provides that the emitter unit comprises a μ-LED anda converter element with a converter material which, excited byexcitation radiation emitted by the μ-LED, emits converted radiation,and that excitation radiation incident on the polarizing element ispolarized and/or absorbed differently when passing through thepolarizing element compared to the converted radiation passing through.

The properties of the three-dimensional photonic structure are thus suchthat the transmission conditions are different for differentwavelengths. In this case, it is conceivable, for example, thatconverted light can pass unhindered through the three-dimensionalphotonic structure while the excitation radiation is deflected. It isalso conceivable that converted radiation only leaves thethree-dimensional photonic structure with a certain polarization.

Furthermore, for some aspects it is conceivable that one of the tworadiations, which have different wavelengths, is discriminated againstby the different properties of the polarizing element in terms ofpolarization and direction of propagation. It is therefore preferablethat in a combination of a μ-LED and a converter element, by which afull conversion is realized, a part of the excitation radiation isfiltered out except for a comparatively small radiation portion with aspecial wavelength, which leads to the fact that a thinner layer of theconverter material can be used.

The structure described herein can be produced in a particularly smallway. In some aspects, for example, an emitter unit with a μ-LED isprovided, and the three-dimensional structure of the polarizationelement is applied directly on the μ-LED chip, preferably on thesemiconductor layer of the μ-LED, through which the generated radiationreaches the light emission surface. According to such embodiment, thethree-dimensional photonic structure is located directly on or in theμ-LED chip.

With such a technical solution, the polarized radiation emission can beused to improve the resolution for the generation of images, andcomponents for beam generation can be made comparatively small. This canbe achieved, for example, by imaging the radiation emitted by severalcomponents or by several illumination units with complementaryproperties via common optics. Optics that are suitable for this purposeare disclosed in this application. Illumination units adapted in thisway are thus particularly suitable for augmented reality applicationsand/or in the field of consumer electronics.

Another aspect relates to a method of manufacturing an optoelectroniccomponent having at least one emitter unit which emits radiation via alight-emitting surface, and having a polarizing element, which adjoinsthe light-emitting surface at least in sections and changes apolarization and/or an intensity of a radiation emanating from theemitter unit when the radiation passes through the polarizing element.

This method can be further developed by using a μ-LED, or an array ofμ-LEDs, as emitter unit, on whose light-emitting surface athree-dimensional photonic structure is applied as polarization element,for example by two-photon lithography or glancing angle deposition,and/or the photonic structure is introduced into a semiconductor layerof the μ-LED adjacent to the light-emitting surface. Thethree-dimensional structure can be dimensioned depending on thewavelength of the radiation emitted by the μ-LED.

Thus, an optoelectronic device based on the principles and structures orobjects disclosed in this application may be used in a device for theproduction of three-dimensional images, in particular for presentationon a display, monitor or screen. In some aspects, the three-dimensionalimpression in a user is based on the fact that light of differentpolarity is directed to the two eyes, the respective light, or thegenerated image or represented objects, being displayed at slightlydifferent positions.

In particular, based on the techniques presented here, three-dimensionalimages can be generated computer-aided for augmented realityapplications or in the automotive sector. It is an advantage here thatthe optoelectronic components disclosed in this application with athree-dimensional photonic structure as polarization element change theradiation characteristic of μ-LEDs with respect to the polarizationproperties and thus a discrimination of different wavelengths due todifferent, wavelength-specific polarization properties or radiationdirections can be achieved.

The polarized radiation can be generated directly on the substrate withthe emitter unit, in particular at the level of a μ-LED chip, or theselectivity can be improved with full conversion. This eliminates theneed for separate elements, which could lead to positioning errors ordeviations. Due to the emission of specifically polarized radiation, theresolution of three-dimensional representations can be improved and atthe same time, the components or illumination units required for imagegeneration can be reduced in size. This can be achieved, for example, byimaging the light of several components with complementary propertiesvia common optics on a display, a screen or even directly on the retinaof a user. Particularly for augmented reality applications and in thefield of consumer electronics, three-dimensional images can be createdby combining complementary polarization elements.

In some other aspects, a photonic structure or a photonic crystal can beused to far-field characteristics of an optoelectronic component can bespecifically altered. Therefore, among other things, an arrangement isproposed which comprises at least one optoelectronic emitter unit, whichemits electromagnetic radiation via a light exit surface. In addition, aphotonic structure is provided for beam shaping of the electromagneticradiation before it exits via the light exit surface, wherein thephotonic structure shapes the electromagnetic radiation in such a waythat the electromagnetic radiation has a certain and defined far field.

The optoelectronic emitter unit is adapted as a μ-LED. Theoptoelectronic emitter unit can also have an array with several μ-LEDs.This provides a photonic structure over a plurality of such μ-LEDs.

Due to the photonic structure, the radiation characteristic of theoptoelectronic emitter unit of the arrangement changes from a Lambertianradiator to a defined radiation characteristic in the far field. Theformulation that the electromagnetic radiation has a certain far fieldthus means in particular that the radiation characteristic is defined inthe far field and differs from the radiation characteristic of a Lambertemitter. The far field refers to a region, which, depending on theapplication, is at least a few centimetres or even a few metres awayfrom the lighting unit so that the magnetic and electronic fields areperpendicular to each other.

The photonic structure may be located, especially in a layer, below thelight-emitting surface and/or between the optoelectronic emitter unitand the light-emitting surface. Thus, the light must pass through itbefore finally leaving the component. The photonic structure can thus beintegrated into the arrangement, making it compact. The photonicstructure can also be integrated into the light-emitting surface, or anend face of the photonic structure can form the light-emitting surface.

In some aspects, the photonic structure is a one-dimensional photonicstructure, especially a one-dimensional photonic crystal. For example,the photonic structure may be configured such that the electromagneticradiation is at least approximately collimated with respect to a firstspatial direction. Thus, a collimated beam can be generated at leastwith respect to the first direction in space.

A collimating optical system can be arranged downstream of the lightexit surface, viewed in the direction of emission, the optical systembeing designed to collimate the electromagnetic radiation in a further,second spatial direction which is orthogonal to the first spatialdirection. The first direction and the second direction can be mutuallyorthogonal directions, which are parallel to the plane light-emittingsurface. Thus, a beam collimated in both directions can be produced,which is directed along the main radiation direction away from thelight-emitting surface and orthogonal to both the first and seconddirections.

According to an embodiment of the invention, the photonic structure, inparticular formed as a one-dimensional photonic crystal, can beconfigured in such a way that a main radiation direction of theelectromagnetic radiation runs at an angle to the normal of thelight-emitting surface, the angle being not equal to zero degrees. Themain radiation direction can thus be inclined to the normal of thelight-emitting surface. A beam collimated in at least one direction canthus, for example, emerge from the light-emitting surface at an angle.

The photonic structure formed as a one-dimensional photonic crystal canbe arranged in a layer below the light-emitting surface, in particulardirectly below. The one-dimensional photonic crystal can thereby have aperiodically repeating sequence of two materials with different opticalrefractive indexes extending in one direction. The materials can eachhave a rectangular or parallelogram-shaped cross-section. The abuttinginterfaces of the materials can be inclined to the light-emittingsurface.

Such a structure can be formed, for example, by etching trenches runningparallel to each other at an angle to the light-emitting surface intothe substrate having the light-emitting surface. The trenches can befilled with a material having a different optical refractive index thanthe substrate material etched away. The angle may depend on theinclination of the trenches to the light-emitting surface, and the widthof the trenches or the width of the substrate material remaining betweenthe trenches influences the wavelengths at which the photonic structureis effective. Typically, the width of the trenches and the width of thesubstrate material remaining between the trenches are adapted to thewavelength of the electromagnetic radiation.

In some aspects, the photonic structure can also be a two-dimensionalphotonic structure, in particular a two-dimensional photonic crystal.One end face of the two-dimensional photonic structure may form thelight-emitting surface of the illumination unit, or the two-dimensionalphotonic structure may be arranged in a layer below the light-emittingsurface.

The two-dimensional structure, in particular a two-dimensional photoniccrystal, can be designed in such a way that it influences theelectromagnetic radiation in such a way that the electromagneticradiation in the far field forms a defined, in particular a discrete,pattern. The illumination unit can thus be used in surface topographysystems, for example for face recognition.

As mentioned above, the photonic structure may be located in a layerbelow the light-emitting surface, or an end face of the photonicstructure may form the light-emitting surface so that the photonicstructure is located directly below the light-emitting surface andencloses it.

The photonic structure can also be formed in a semiconductor layer ofthe optoelectronic emitter unit.

The optoelectronic emitter unit may comprise a layer of convertermaterial and the photonic structure may be formed in the layer ofconverter material or in a layer between the layer of converter materialand the light-emitting surface.

The optoelectronic emitter unit can have at least one optoelectroniclaser, such as a VCSEL (vertical-cavity surface-emitting laser). A fieldof several lasers is also conceivable.

BRIEF DESCRIPTION OF THE DRAWINGS

In the following section, some of the above-mentioned and summarizedaspects are explained in more detail using various explanations andexamples.

FIG. 1A shows a diagram illustrating some requirements for so-calledμ-displays or micro-displays of different sizes with respect to thefield of view and pixel pitch of the μ-display;

FIG. 1B shows a diagram of the spatial distribution of rods and cones inthe human eye;

FIG. 1C shows a diagram of the perceptual capacity of the human eye withassigned projection areas;

FIG. 1D is a figure showing the sensitivity of the rods and cones overthe wavelength;

FIG. 2A is a diagram illustrating some requirements for micro-displaysof different sizes in terms of the field of view and the angle ofcollimation of a pixel of the μ-display;

FIG. 2B illustrates an exemplary execution of a pixel arrangement toillustrate the parameters used in FIGS. 1A and 2A;

FIG. 3A shows a diagram illustrating the number of pixels requireddepending on the field of view for a specific resolution;

FIGS. 3B-1 and 3B-2 are a table of preferred applications for μ-LEDarrays;

FIG. 4A shows a principle representation of a μ-LED display withessential elements for light generation and light guidance;

FIG. 4B shows a schematic representation of a μ-LED array with similarμ-LEDs;

FIG. 4C is a schematic representation of a μ-LED array with μ-LEDs ofdifferent light colors;

FIG. 5A and FIG. 5B show two examples of a structure or beamline andcollimation;

FIG. 6 shows a μ-LED pixel where the light emission is already directedby a specially formed reflector material;

FIG. 7 shows an optical pixel element with a spherical reflector elementand control electronics according to some aspects of the proposedconcept;

FIG. 8 shows a second embodiment of a pixel element with a reflectorelement designed as a layer and a passivation layer according to someaspects of the proposed concept;

FIG. 9 shows a third embodiment of a pixel element with light-absorbingcoatings on a display side and an assembly side of the carrier substrateaccording to some aspects of the proposed concept;

FIG. 10 forms a pixel element with a roughened display side of thecarrier substrate;

FIGS. 11A and 11B are embodiments based on some of the aspects revealedhere, with light absorbing layers to minimize crosstalk and a colorfilter element on the display side of the carrier substrate;

FIGS. 12A and 12B show embodiments of a pixel element with IGZO- orLIPS-based drive electronics on the assembly side of the carriersubstrate and optional diffuser layer according to some aspects of theproposed concept;

FIG. 13 shows a cross-section and top view of a pixel cell with threeμ-LEDs of different colors and a reflector element;

FIG. 14 shows a method for manufacturing an optical pixel element asdescribed above;

FIG. 15A shows on the top a cross-sectional view of an exemplary μ-LEDand on the bottom a perspective view of the optoelectronic device with aphotonic structure;

FIG. 15B shows a cross-sectional view of another μ-LED with photonicstructure according to some suggested aspects;

FIG. 15C shows on the left side a more detailed cross-sectional view ofanother optoelectronic device and on the right side a more schematiccross-sectional view of the optoelectronic device;

FIG. 15D is a cross-sectional view of a μ-LED with planar surface andphotonic structure;

FIG. 15E shows another embodiment of a μ-LED with photonic structure incross-sectional view;

FIG. 15F illustrates another embodiment of a μ-LED with photonicstructure in cross-sectional view according to some aspects of theproposed concept;

FIG. 16 shows an embodiment of a method for producing one of thestructures shown in FIGS. 15D to 15E;

FIG. 17 illustrates a top view and sectional view of an optoelectronicdevice with a μ-LED and a converter element according to some aspects ofsimultaneous light shaping and light conversion;

FIG. 18 shows a cross-section through an optoelectronic component in afurther version according to some aspects of the proposed concept;

FIG. 19 is a top view and sectional view of another component;

FIG. 20 shows a cross-section through a component with a μ-LED and aconverter element according to some aspects of light shaping and lightconversion;

FIGS. 21A and 21B show a μ-display with several light-emitting units anda photonic structure in a top view and cross section according to someaspects of the concept presented;

FIGS. 22A and 22B represent a second embodiment of a μ-display with aphotonic structure in a top view and cross-section according to someaspects of the presented concept;

FIGS. 23A and 23B show a third embodiment of a μ-display with severalμ-LEDs of a photonic structure in a top view and as a cross-sectionaccording to some aspects of the presented concept;

FIGS. 24A and 24B are part of a fourth embodiment of a μ-display with aphotonic structure in a top view and as a cross-section according tosome aspects of the concept presented;

FIGS. 25A and 25B show a fifth embodiment of a μ-display with a photonicstructure in a top view and as a cross-section according to some aspectsof the presented concept;

FIGS. 26A and 26B illustrate a sixth embodiment of a μ-display with aphotonic structure in a top view and as a cross-section according tosome aspects of the concept presented;

FIGS. 27A and 27B show a seventh embodiment of a μ-display with aphotonic structure in a top view and as a cross section according tosome aspects of the presented concept;

FIGS. 28A and 28B illustrate an eighth embodiment of a μ-display of aphotonic structure in a top view and as a cross-section;

FIGS. 29A and 29B show a ninth embodiment of a μ-display of a photonicstructure in a top view and as a cross-section according to some aspectsof the presented concept;

FIG. 30 shows a cross-sectional view of another variant of a deviceaccording to the invention;

FIG. 31 shows an arrangement of an optoelectronic component with anemitter unit having a light-emitting surface to which a polarizingelement with a three-dimensional photonic structure is applied;

FIG. 32 illustrates a representation of a three-dimensional photonicstructure with a large number of spiral-shaped structural elements;

FIG. 33 shows another embodiment of an optoelectronic device with anemitter unit and a polarization element with a three-dimensionalphotonic structure;

FIG. 34 shows an optoelectronic device with an emitter unit and athree-dimensional photonic structure into which converter material isfilled;

FIG. 35 illustrates a perspective view of a first variant of anarrangement with an emitter unit, which has a photonic structure forgenerating a specific far field;

FIG. 36 shows a sectional view of a second variant of an arrangementwith an emitter unit to illustrate further aspects of the proposedprinciple;

FIG. 37 shows an arrangement of a plurality of arrangements according tothe two preceding figures;

FIG. 38 shows a perspective view of a third variant of an arrangementwith an emitter unit, which has a photonic structure to generate adefined far field;

FIG. 39 illustrates a block diagram of a surface topography detectionsystem with an arrangement according to one of the preceding figures;

DETAILED DESCRIPTION

Augmented reality is usually generated by a dedicated display whoseimage is superimposed on reality. Such device can be positioned directlyin the user's line of sight, i.e. directly in front of it.Alternatively, optical beam guidance elements can be used to guide thelight from a display to the user's eye. In both cases, the display maybe implemented and be part of the glasses or other visually enhancingdevices worn by the user. Googles™ Glasses is an example of such avisually augmenting device that allows the user to overlay certaininformation about real world objects. For the Google™ glasses, theinformation was displayed on a small screen placed in front of one ofthe lenses. In this respect, the appearance of such an additional deviceis a key characteristic of eyeglasses, combining technical functionalitywith a design aspect when wearing glasses. In the meantime, usersrequire glasses without such bulky or easily damaged devices to provideadvanced reality functionality. One idea, therefore, is that the glassesthemselves become a display or at least a screen on or into which theinformation is projected.

In such cases, the field of vision for the user is limited to thedimension of the glasses. Accordingly, the area onto which extendedreality functionality can be projected is approximately the size of apair of spectacles. Here, the same, but also different information canbe projected on, into or onto the two lenses of a pair of spectacles.

In addition, the image that the user experiences when wearing glasseswith augmented reality functionality should have a resolution thatcreates a seamless impression to the user, so that the user does notperceive the augmented reality as a pixelated object or as alow-resolution element. Straight bevelled edges, arrows or similarelements show a staircase shape that is disturbing for the user at lowresolutions.

In order to achieve the desired impression, two display parameters areconsidered important, which have an influence on the visual impressionfor a given or known human sight. One is the pixel size itself, i.e. thegeometric shape and dimension of a single pixel or the area of 3subpixels representing the pixel. The second parameter is the pixelpitch, i.e. the distance between two adjacent pixels or, if necessary,subpixels. Sometimes the pixel pitch is also called pixel gap. A largerpixel pitch can be detected by a user and is perceived as a gap betweenthe pixels and in some cases causes the so-called fly screen effect. Thegap should therefore not exceed a certain limit.

The maximum angular resolution of the human eye is typically between0.02 and 0.03 angular degrees, which roughly corresponds to 1.2 to 1.8arc minutes per line pair. This results in a pixel gap of 0.6-0.9 arcminutes. Some current mobile phone displays have about 400 pixels/inch,resulting in a viewing angle of approximately 2.9° at a distance of 25cm from a user's eye or approximately 70 pixels/° viewing angle and cm.The distance between two pixels in such displays is therefore in therange of the maximum angular resolution. Furthermore, the pixel sizeitself is about 56 μm.

FIG. 1A illustrates the pixel pitch, i.e. the distance between twoadjacent pixels as a function of the field of view in angular degrees.In this respect, the field of view is the extension of the observableworld seen at a given moment. This is because human vision is defined asthe number of degrees of the angle of view during stable fixation of theeye.

In particular, humans have a forward horizontal arc of their field ofvision for both eyes of slightly more than 210°, while the vertical arcof their field of vision for humans is around 135°. However, the rangeof visual abilities is not uniform across the field of vision and canvary from person to person.

The binocular vision of humans covers approximately 114° horizontally(peripheral vision), and about 90° vertically. The remaining degrees onboth sides have no binocular area but can be considered part of thefield of vision.

Furthermore, color vision and the ability to perceive shapes andmovement can further limit the horizontal and vertical field of vision.The rods and cones responsible for color vision are not evenlydistributed.

This point of view is shown in more detail in FIGS. 1B to 1D. In thearea of central vision, i.e. directly in front of the eye, as requiredfor Augmented Reality applications and partly also in the automotivesector, the sensitivity of the eye is very high both in terms of spatialresolution and in terms of color perception.

FIG. 1B shows the spatial density of rods and cones per mm² as afunction of the fovea angle. FIG. 1C describes the color sensitivity ofcones and rods as a function of wavelength. In the central area of thefovea, the increased density of cones (L, S and M) means that bettercolor vision predominates. At a distance of about 25° around the fovea,the sensitivity begins to decrease and the density of the visual cellsdecreases. Towards the edge, the sensitivity of color vision decreases,but at the same time contrast vision by means of the rods remains over alarger angular range. Overall, the eye develops a radially symmetricalvisual pattern rather than a Cartesian visual pattern. A high resolutionfor all primary colors is therefore required, especially in the center.At the edge it may be sufficient to work with an emitter adapted to thespectral sensitivity of the rods (max. sensitivity at 498 nm, see FIG.1D and the sensitivity of the eye).

FIG. 1C shows the different perceptual capacity of the human eye bymeans of a graph of the angular resolution A relative to the angulardeviation a from the optical axis of the eye. It can be seen that thehighest angular resolution A is in an interval of the angular deviationa of +/−2.5°, in which the fovea centralis 7 with a diameter of 1.5 mmis located on the retina 19. In addition, the position of the blind spot22 on the retina 19 is sketched, which is located in the area of theoptic nerve papilla 23, which has a position with an angular deviation aof about 15°.

The eye compensates this non-constant density and also the so-calledblind spot by small movements of the eye. Such changes in the directionof vision or focus can be counteracted by suitable optics and trackingof the eye.

Furthermore, even with glasses, the field of vision is furtherrestricted and, for example, can be approximately in the range of 80°for each lens.

The pixel pitch in FIG. 1A on the Y-axis is given in μm and defines thedistance between two adjacent pixels. The various curves C1 to C7 definethe diagonal dimension of a corresponding display from 5 mm toapproximately 35 mm. For example, curve C1 corresponds to a display withthe diagonal size of 5 mm, i.e. a side length of approximately 2.25 mm.For a field of view of approximately 80°, the pixel pitch of a displaywith a diagonal size of 5 mm is in the range of 1 μm. For largerdisplays like curve C7 and 35 mm diagonal size, the same field of viewcan be implemented with a pixel pitch of approximately 5 μm.

Nevertheless, the curves in FIG. 1A illustrate that for larger fields ofview, which are preferred for extended reality applications, very highpixel densities with small pixel pitch are required if the well-knownfly screen effect is to be avoided. One can now calculate the size ofthe pixel for a given number of pixels, a given field of view and agiven diagonal size of a μ-display.

Equation 1 shows the relationship between dimension D of a pixel, pixelpitch pp, number N of pixels and the edge length d of the display. Thedistance r between two adjacent pixels calculated from their respectivecenters is given by

r=d/2+pp+d/2.

D=d/N−pp

N=d/(D+pp)  (1)

Assuming that the display (e.g. glasses) is at a distance of 2.54 cm (1inch) from the eye, the distance r between two adjacent pixels for anangular resolution of 1 arcminute as roughly estimated above is given by

r=tan( 1/60°)*30 mm

r=8.7 μm

The size of a pixel is therefore smaller than 10 μm, especially if somespace is required between two different pixels. With a distance, rbetween two pixels and a display with the size of 15 mm×10 mm, 1720×1150pixels can be arranged on the surface.

FIG. 2B shows an arrangement, which has a carrier 21 on which a largenumber of pixels, 20 and 20 a to 20 c are arranged. Pixels 20 arrangedside by side have the pixel pitch pp, while pixels 20 a to 20 c areplaced on carrier 21 with a larger pixel pitch pp. The distance betweentwo pixels is given by the sum of the pixel pitch and half the size foreach adjacent pixel. Each of the pixels 20 is configured so that itsillumination characteristic or its emission vector 22 is substantiallyperpendicular to the emission surface of the corresponding LED.

The angle between the perpendicular axes to the emission surface of theLED and the beam vector is defined as the collimation angle. In theexample of emission vector 22, the collimation angle of LEDs 20 isapproximately zero. LED 20 emits light that is collinear and does notwiden significantly.

In contrast, the collimation angle of the emission vector 23 of the LEDpixels 20 a to 20 c is quite large and in the range of approximately45°. As a result, part of the light emitted by LED 20 a overlaps withthe emission of an adjacent LED 20 b.

The emission of the LEDs 20 a to 20 c is partially overlapping, so thatits superposition of the corresponding light emission occurs. In casethe LEDs emit light of different colors, the result will be a colormixture or a combined color. A similar effect occurs between areas ofhigh contrast, i.e. when LED 20 a is dark while LED 20 b emits a certainlight. Because of the overlap, the contrast is reduced and informationabout each individual position corresponding to a pixel position isreduced.

In displays where the distance to the user's eye is only small, as inthe applications mentioned above, a larger collimation angle is ratherannoying due to the effects mentioned above and other disadvantages. Auser is able to see a wide collimation angle and may perceive displayedobjects in slightly different colors blurred or with reduced contrast.

FIG. 2A illustrates in this respect the requirement for the collimationangle in degrees against the field of view in degrees, independent ofspecific display sizes. For smaller display sizes such as the one incurve C1 (approx. 5 mm diagonal), the collimation angle increasessignificantly depending on the field of view.

As the size of the display increases, the collimation angle requirementschange drastically, so that even for large display geometries such asthose illustrated in curve C7, the collimation angle reaches about 10°for a field of view of 100°. In other words, the collimation anglerequirements for larger displays and larger fields of view areincreasing. In such displays, light emitted by a pixel must be highlycollimated to avoid or reduce the effects mentioned above. Consequently,strong collimation is required when displays with a large field of vieware to be made available to a user, even if the display geometry isrelatively large.

As a result of the above diagrams and equations, one can deduce that therequirements regarding pixel pitch and collimation angle becomeincreasingly challenging as the display geometry and field of view grow.As already indicated by equation 1, the dimension of the displayincreases strongly with a larger number of pixels. Conversely, a largenumber of pixels is required for large fields of view if sufficientresolution is to be achieved and fly screens or other disturbing effectsare to be avoided.

FIG. 3A shows a diagram of the number of pixels required to achieve anangular resolution of 1.3 arc minutes. For a field of view ofapproximately 80°, the number of pixels exceeds 5 million. It is easy toestimate that the size of the pixels for a QHD resolution is well below10 μm, even if the display is 15 mm×10 mm. In summary, advanced realitydisplays with resolutions in the HD range, i.e. 1080p, require a totalof 2.0736 million pixels. This allows a field of view of approximately50° to be covered. Such a quantity of pixels arranged on a display sizeof 10×10 mm with a distance between the pixels of fpm results in a pixelsize of about 4 μm.

In contrast, the table in FIG. 3B shows several application areas inwhich μ-LED arrays can be used. The table shows applications (use case)of μ-LED arrays in vehicles (Auto) or for multimedia (MM), such asautomotive displays and exemplary values regarding the minimum andmaximum display size (min. and max. size X Y [cm]), the pixel density(PPI) and the pixel pitch (PP [μm]) as well as the resolution(Res.-Type) and the distance of the viewer (Viewing Distance [cm]) tothe lighting device or display. In this context, the abbreviations “verylow res”, “low res”, “mid res” and “high res” have the followingmeaning:

very low res pixel pitch approx. 0.8-3 mm

low res Pixel pitch approx. 0.5-0.8 mm

mid res Pixel pitch approx. 0.1-0.5 mm

high res Pixel pitch less than 0.1 mm

The upper part of the table, entitled “Direct Emitter Displays”, showsinventive applications of μ-LED arrays in displays and lighting devicesin vehicles and for the multimedia sector. The lower part of the table,titled “Transparent Direct Emitter Displays”, names various applicationsof μ-LED arrays in transparent displays and transparent lightingdevices. Some of the applications of μ-displays listed in the table areexplained in more detail below in the form of embodiments.

The above considerations make it clear that challenges are considerablein terms of resolution, collimation and field of view suitable forextended reality applications. Accordingly, very high demands are placedon the technical implementation of such displays.

Conventional techniques are configured for the production of displaysthat have LEDs with edge lengths in the range of 100 μm or even more.However, they cannot be automatically scaled to the sizes of 70 μm andbelow required here. Pixel sizes of a few μm as well as distances of afew μm or even less come closer to the order of magnitude of thewavelength of the generated light and make novel technologies inprocessing necessary.

In addition, new challenges in light collimation and light direction areemerging. Optical lenses, for example, which can be easily structuredfor larger LEDs and can also be calculated using classical optics,cannot be reduced to such a small size without the Maxwell equations.Apart from this, the production of such small lenses is hardly possiblewithout large errors or deviations. In some variants, quantum effectscan influence the behaviour of pixels of the above-mentioned size andhave to be considered. Tolerances in manufacturing or transfertechniques from pixels to sub mounts or matrix structures are becomingincreasingly demanding. Likewise, the pixels must be contacted andindividually controllable. Conventional circuits have a spacerequirement, which in some cases exceeds the pixel area, resulting in anarrangement and space problem.

Accordingly, new concepts for the control and accessibility of pixels ofthis size can be quite different from conventional technologies.Finally, a focus is on the power consumption of such displays andcontrollers. Especially for mobile applications, a low power consumptionis desirable.

In summary, for many concepts that work for larger pixel sizes,extensive changes must be made before a reduction can be successful.While concepts that can be easily up scaled to LEDs at 2000 μm for theproduction of LEDs in the 200 μm range, downscaling to 20 μm is muchmore difficult. Many documents and literature that disclose suchconcepts have not taken into account the various effects and increaseddemands on the very small dimensions and are therefore not directlysuitable or limited to pixel sizes well above 70 μm.

In the following, various aspects of the structure and design of μ-LEDsemiconductors, aspects of processing, light extraction and lightguidance, display and control are presented. These are suitable anddesigned to realize displays with pixel sizes in the range of 70 μm andbelow. Some concepts are specifically designed for the production, lightextraction and control of μ-LEDs with an edge length of less than 20 μmand especially less than 10 μm. It goes without saying, and is evendesired, that the concepts presented here can and should be combinedwith each other for the different aspects. This concerns for example aconcept for the production of a μ-LED with a concept for lightextraction. In concrete terms, a μ-LED implemented by means of methodsto avoid defects at edges or methods for current conduction or currentconstriction can be provided with light extraction structures based onphotonic crystal structures. Likewise, a special drive can also berealized for displays whose pixel size is variable. Light guidance withpiezoelectric mirrors can be realized for μ-LEDs displays based on theslot antenna aspect or on conventional monolithic pixel matrices.

In some of the following embodiments and described aspects, additionalexamples of a combination of the different embodiments or individualaspects thereof are suggested. These are intended to illustrate that thevarious aspects, embodiments or parts thereof can be combined with eachother by the skilled person. Some applications require specially adaptedconcepts; in other applications, the requirements for the technology aresomewhat lower. Automotive applications and displays, for example, mayhave a longer pixel edge length due to the generally somewhat greaterdistance to a user. Especially there, besides applications of extendedreality, classical pixel applications or virtual reality applicationsexist. This is in the context of this disclosure for the realization ofμ-LED displays, whose pixel edge length is in the range of 70 μm andbelow, also explicitly desired.

A general illustration of the main components of a pixel in a μ-displayis shown schematically in FIG. 4A. It shows an element 60 as a lightgenerating and light emitting device. Various aspects of this aredescribed in more detail below in the section on light generation andprocessing. Element 60 also includes basic circuits, interconnects, andsuch to control the illumination, intensity, and, when applicable, colorof the pixel. Aspects of this are described in more detail in thesection on light control. Apart from light generation, the emitted lightmust be collimated. For this purpose, many pixels in microdisplays havesuch collimation functionality in element 60. The parallel light inelement 63 is then fed for light guidance into some optics 64, forfurther shaping and the like. Light collimation and optics suitable forimplementing pixels for microdisplays are described in the section onlight extraction and light guidance.

The pixel device of FIG. 4A illustrates the different components andaspects as separate elements. An expert will recognize that manycomponents can be integrated into a single device. In practice, theheight of a μ-display is also limited, resulting in a desired flatarrangement.

After light has been generated, it must be collimated and directionallycoupled out as far as possible. Therefore the following explanationsconcern different aspects of light extraction.

FIGS. 5A and 5B disclose some principles regarding the collimation anddirection of light emitted by individual pixels. FIG. 5A shows a carrier50, which also acts as a mirror by reflecting all light emitted by theLED 51 arranged on the carrier. Two adjacent LEDs are about 6 μm apartand about 3 μm high. Their diameter is in the range of 6 μm. Eachindividual pixel emits light similar to a Lambert spotlight.Consequently, they are completely covered with a transparent materialwith a refractive index of about n=1.5.

A hemisphere 53 of the same material with a radius of approximately 10μm is arranged on each micropixel. Each hemisphere 53 covers the area ofthe underlying pixel 51 and extends to about half the distance to thenext pixel. Because of the refractive index and geometry, thehemispheres are configured to collimate the light emitted by theindividual pixels.

FIG. 5B shows an alternative concept for collimating the light emittedby the pixels. Similar to the above, the micropixels are arranged atequal distances from each other. Between each pixel, a pyramid 52 isplaced on the support 50. The pyramids 52 are formed of highlyrefractive material and have distance D between their tips. The heightof the apex of each pyramid is chosen so that light emitted at an angleless than 45° from the light-emitting surface is reflected on thesidewalls of the pyramid as indicated. By using the elements shown inFIG. 5B, light emitted by micropixels 51 can be parallelized to acertain extent, which improves its collimation. However, as the sizedecreases, it becomes increasingly difficult to shape elements 52 and 53and to place them directly above the micropixels.

FIG. 6 illustrates an example of a pixel for which, in one aspect, arear decoupling is provided by shaping the pixel as a hemisphere andsurrounding it with reflective material to shape the emitted light. Thepixel is shaped as a half-dome within an n-doped first semiconductormaterial 800. A first contact 801 on a first side of material 800 servesas the n-contact for the corresponding pixel. A second contact 802 canbe used for a variety of pixels.

Thus, it is possible to arrange the plurality of pixels next to eachother to form a μ-display. Within the half-dome area of the pixel, anactive layer 803 is arranged. The active layer is located in the upperthird of the half-dome forming the pixel and is formed by a p-dopedlayer 804 deposited on the n-doped material in the half-dome. Otheractive layers such as quantum wells or structures mentioned in thisdisclosure are possible. In order to form the smallest possible regionwhere recombination occurs, a current confinement process can be used.This keeps charge carriers away from the edge and the recombination areabecomes smaller.

A reflective layer 805 is applied to the sidewalls and also to the uppersurface of the material 800. The p-contact 801 is applied to thereflective layer 805. The reflective layer 805 also includes aninsulating layer (not shown) to prevent a short circuit between thep-contact and the material 800. P-contact material 801 is in directcontact with the p-doped layer 804 through a gap in the reflective layeron the half-dome forming the pixel. As a result, the insulating layer onthe reflective layer and the gap in the reflective layer causes carrierinjection only at the tip of the half-dome. A current broadening layercan also be applied within the p-doped layer 804.

Recombination of charge carriers occurs in the active region 803 Lightemitted from the active region towards the side is reflected at thereflective layer towards the output surface TA. The shape of thehalf-dome is parabolic in some examples. The shape should be chosen tosupport collinearity for light generated within the active region. Insome applications, other elements for guiding light, such as photoniccrystal structures or similar are then arranged on the exit surface.

The following aspects deal with a different point of view in contrast toa direct improvement of the directionality of the emitted light. Thefollowing examples are intended for the creation of a Lambert radiator.However, it is known by the expert that other shapes on reflectorelements influence the beam-shaping. Special designs thus create a μ-LEDwith rear output, which can be directed at the same time.

FIG. 7 shows an embodiment of a pixel element 10 with a reflectorelement 18 according to the invention. First of all, a carrier substrate12 is also provided here, which often has a large number of μ-LEDs 16arranged next to each other on an assembly side 20 of the carriersubstrate 12. The carrier substrate 12 is usually provided with anelectronic control unit 24, which is used to control the individualμ-LEDs 16. For this purpose, electrically conductive connections (notshown) may be provided between the control electronics 24 and theindividual μ-LEDs 16. In other cases, as shown below, the carriersubstrate can also be transparent or have other structures for reshapingthe light.

The reflector element 18 here is designed like a dome and surrounds theμ-LED 16 at least on the side where the μ-LED 16 emits light 14. Forexample, if the μ-LED 16 emits light 14 in a direction away from thecarrier substrate 12, this light hits a surface of the reflector element18 directed towards the μ-LED 16, is reflected there and returnedtowards the assembly side 20 of the carrier substrate 12. If necessary,the light propagates with refraction at the interface of the assemblyside 20 over a cross section of the carrier substrate 12 in thedirection of a display side 22 of the carrier substrate 12 and iscoupled out there, if necessary with repeated refraction or diffraction.

The reflector element 18 should have the advantageous shape andproperties that light 14 is incident at an angle of incidence 26 asperpendicular as possible relative to a carrier substrate plane 28 onthe placement side 20 of the carrier substrate 12. Among other things,this should serve to minimize losses due to total reflection within thecarrier substrate 12 as well as unfavourable angles when decoupling fromdisplay side 22 of carrier substrate 12. This angle of incidence 26should be as small as possible, also to minimize crosstalk betweenadjacent pixel elements 10.

FIG. 8 shows another example of a pixel element 10 according to theinvention with a reflector element 18 configured as a layer on or arounda μ-LED 16. This embodiment variant can be useful in that the reflectorelement 18 can be processed directly onto a surface of the μ-LED 16, forexample as a metallic layer. Various materials can be used for thereflector element 18, such as metallic materials, metal alloys or oxidesor other suitable compounds that can be applied using the availablemanufacturing processes. FIG. 6 shows a similar embodiment, in which theμ-LED is made directly from the same material as the carrier substrate.In addition, the reflector element has a specific shape and design.However, the various aspects of FIG. 6 can also be combined with theembodiments shown in FIGS. 7 to 8, among others, and disclosed here.

In addition, a passivation layer 32 is provided at the mesa edges 30between the μ-LED 16 and the layer of the reflector element 18. Thispassivation layer 32 has light-absorbing or at least light-blockingproperties so that light 14 emitted by the μ-LED in the direction of thecarrier substrate plane 28 or in the direction of the mesa edges 30 isattenuated or absorbed. This is to prevent light 14 from passing over inthe direction of an adjacent pixel element 10 and causing crosstalk. Inaddition, the passivation layers 32 can be configured to causebeam-shaping of the emitted light 14.

FIG. 9 shows a pixel element according to the invention withlight-absorbing coatings 34 on a display side 20 and an assembly side 22of the carrier substrate 12. This embodiment features a sphericalreflector element 18 surrounding a μ-LED 16, which is arranged on theplacement side 20 of the carrier substrate 12. According to this aspect,the carrier substrate 12 is adapted to be transparent or at leastpartially transparent so that light 14 can propagate within the carriersubstrate 12.

In order to improve the dark impression and contrast of a display,light-absorbing layers 34 are provided according to this embodiment,which are applied here outside the reflector element 18 on the carriersubstrate 12 on the assembly side 20 and/or on the display side 22. Onthe one hand, this can prevent light 14 from being coupled out outside adesired active area of the pixel element. On the other hand, anadvantageous effect can be that light 14, which propagates inside thecarrier substrate 12, is not coupled out outside the desired area ondisplay side 22, but is absorbed or attenuated. For an observer, thelight-absorbing layers 34 can be recognized as clearly inactive or blackor dark, and due to the better optical demarcation compared to theactive luminous areas, improved contrast properties of a display can beachieved.

FIG. 10 illustrates in a simplified way a further version of a pixelelement 10 according to the invention. In its basic structure, pixelelement 10 corresponds to the examples already shown in FIGS. 7 to 9.Here, a μ-LED 16 is provided on a carrier substrate 12, which issurrounded by a reflector element 18. By reflecting the light 14 at thereflector element 18, light 14 propagates through the carrier substrate12 and reaches a display page 22 of the carrier substrate 12.

Here it is desirable that as much of the light 14 that has passedthrough carrier substrate 12 is coupled out of carrier substrate 12 viadisplay screen 22. Here, a roughened surface 36 can cause an improvedout-coupling of light 14. More generally speaking, the surface of thedisplay side 22 comprises a structuring, which has additionalmicrostructures at an angle to each other which deviate in their anglefrom the alignment parallel to a carrier substrate plane 28 and can thuscause additional out-coupling.

FIG. 11A shows a pixel element 10, according to the invention, with acolor filter element 38 on the display side of the carrier substrate 12and light-absorbing coatings 34. While the basic structure of the pixelelement 10 corresponds to a large extent to that of the previousfigures, light-absorbing coatings 34 are also provided here, which areprovided both on an assembly side 20 and on a display side 22 of thecarrier substrate 12 outside an area of the reflector element 18. Inaddition, a color filter element 38 is provided here, which is arrangedon the display side 22 of the carrier substrate 12 opposite thereflector element 18. For example, a red μ-LED can be provided with acorresponding red color filter element 38. The same appliesanalogueously to green color filter elements 38 together with greenμ-LEDs and, for example, to blue color filter elements 38 together withblue μ-LEDs and the respective emitter chips 16. The advantages here arelower reflectivity and an improved black impression. Here, too, thelight-absorbing layers 34 absorb unwanted light components 14 thatpropagate within the carrier substrate 12.

In an alternative embodiment, again with reference to FIG. 11A, element38 may also be a color conversion element to convert light of a firstwavelength to a second wavelength. The light emitted by the μ-LED 16 andreflected by the reflector element 18 strikes the converter element andis converted there. The basic colors can be produced in this way byusing different converter dyes.

FIG. 11B shows another example of a pixel element 10, where two adjacentpixel elements 10 are arranged on the carrier substrate. Between thesetwo pixel elements, light absorbing layers 34 are provided on thedifferent surfaces of the carrier substrate. This can be used inparticular to minimize crosstalk. Depending on the arrangement anddesign of the μ-LED 16, there is a gap between the μ-LED 16 and thesurrounding reflector element 18, which can act as an aperture oraperture edge. This can mean that light 14 emerges through this apertureat a small angle relative to the carrier substrate plane 28 and can passthrough the carrier substrate 12 at an angle in the direction of theadjacent pixel element 10.

To prevent this crosstalk, light-absorbing layers 34 are providedbetween the two pixel elements 10 and between the two adjacent reflectorelements 18, respectively. These can be arranged on an assembly side 20of the carrier substrate 12, but also on a display side 22 of thecarrier substrate 12. The light-absorbing layers 34 attenuate oreliminate the then unwanted light components 14 and can thus improve thecontrast of a display.

In FIG. 12A, reference is made to the aspect of the control electronics24 of a pixel element 10 according to the invention. These may beadapted as part of the carrier substrate 12, with transistor structures,for example, being provided as part of the substrate 12. For thematerial of the carrier substrate 12, various materials can beconsidered, such as amorphous silicon, but also IGZO or LTPS. IGZOstands for indium gallium zinc oxide and has partially transparentproperties for light and is comparatively inexpensive to manufacture.

If an electronic control unit 24 is designed on the basis of IGZO, it isalso conceivable according to an example that the electronic controlunit 24 can be arranged within an inner area of a reflector element 18(not shown here). This possibility is based in particular on the atleast partial light transmission of the IGZO material. According toanother example, 24 LTPS is used as the basis for the controlelectronics 24 and LTPS as the material for the carrier substrate 12.LTPS stands for Low Temperature Poly Silicon and can have betterelectrical properties than IGZO, but with more light absorbingproperties.

LTPS can be used for both p-transistors and n-transistors, whereas IGZOis only suitable for p-transistors. An arrangement of the controlelectronics 24, based on LTPS, must therefore be provided here outside areflector element 18. A further alternative can be seen in the use ofso-called μICs. These are often used together with silicon-basedsubstrates and usually have light-absorbing properties.

A challenge here may lie in miniaturizing these ICs, whereby theelectrical performance of the μICs is often higher than that of othervariants. Here, too, an arrangement would, according to an example, bemade outside an area of a reflector element 18 on the assembly side 20of the carrier substrate 12. Contacting of the emitter chip 16 can beachieved, for example, via a metallic contact pad on the carriersubstrate 12 or via transparent ITO (indium tin oxide).

FIG. 12B shows a pixel element 10 according to the invention with apartial coating of a diffuser layer 40 on the reflector element 18. Thespecial feature of the pixel element 10 shown in this embodiment can beseen in a special embodiment of the reflector element 18. Here, adiffuser layer 40 is provided on the lateral inner surfaces of thereflector element 18 (here especially the area 18B). This diffuser layer40 is intended to cause an increased deflection of the emitted light 14and a more advantageous deflection of the light 14 in the direction ofthe carrier substrate 12. It can be advantageous here to provide athinner or completely missing diffuser layer 40 in an area 18A of thereflector located vertically directly above the emitter chip.

In particular, this diffuser layer 40 can be made flat or even in thisarea 18A in order to focus the most direct possible back reflection oflight emitted transversely to the carrier substrate plane 28approximately vertically in the direction of the placement side 20 ofthe carrier substrate 12. A relatively thin diffuser layer 40 can besufficient for this purpose, since μ-LEDs, due to their properties andconstruction, come closer to a Lambertian radiation pattern thanprevious LED technologies. Materials that can be used for this purposeinclude Al₂O₃ or TiO₂.

FIG. 13 shows another pixel cell in cross-section and top view. Thepixel cell comprises three individual μ-LEDs 16 r, 16 g and 16 b. Theseare designed to emit the respective basic colors red, green and blueduring operation. In this embodiment, the three μ-LEDs are arranged inthe corners of a right-angled triangle. However, other arrangements arealso possible, for example in a row. Each μ-LED is adapted as a verticalμ-LED, i.e. a common contact is located on the side of the μ-LEDs facingaway from the carrier substrate. The μ-LEDs can be individuallycontrolled and can be manufactured, for example, in some versions asshown in FIGS. 49 to 54. Other designs are also conceivable, for exampleas individual μ-LED modules with or without redundancy. In theillustration on the right, a common transparent cover contact 17 isprovided for this purpose, which either completely or at least partiallycovers the μ-LEDs and thus makes electrical contact. The sidewalls ofthe μ-LED are insulated and are not connected to the cover electrode 17.In addition, a reflector element 18 is provided which surrounds each ofthe three μ-LEDs and thus forms a complete pixel.

Light, which is thus emitted in the direction of the reflector element,is reflected by the carrier substrate where it hits a photonic structure19, which is partly incorporated in the carrier substrate. The photonicstructure 19 is designed to redirect the emitted light and emit it as acollimated light beam. Various embodiments of such photonic structuresare disclosed in this application, for example in FIG. 17 to 20, 31 to39 or even 15A to 15C.

The photonic structure can also be omitted depending on the application.For automotive applications, a Lampertian radiation pattern may be moredesirable, in which case it is omitted. In the field of AugmentedReality a strong directionality may be desired, which is achieved by theadditional photonic structure. In addition to the photonic structure, aconverter material can also be provided in addition to the structure oralternatively. In the automotive sector, such directional lightapplications with white or other colored light are possible.

Finally, FIG. 14 shows a process 100 for the production of a pixelelement 10. First, one or more μ-LEDs are attached to one side of a flatcarrier substrate. The attachment is preceded by a correspondingtransfer. Details are disclosed in this application.

This is followed in step 120 by creating a reflector element, forexample as a reflective layer of the μ-LED. According to an example,before step 110, a display side 22 of the carrier substrate 12 isprocessed to produce a roughening 36 or rough micro-structuring of thesurface of the display side 22.

One way to reduce the emission angle of μ-LEDs is to indicate structureson the emission surface that reduce the propagation of light parallel tothe emission surface. This can be achieved by photonic structures. Thephotonic crystal structure is basically not limited to a certainmaterial system. The following examples and embodiments will givedifferent ones, which are not limited to a specific design, but aresuitable for all embodiments and designs disclosed herein. Furthermore,different semiconductor material systems can be used for the μ-LEDs,especially on GaN, AlInGaP, AlN or InGaAs basis. FIGS. 15A to 15Cillustrate different aspects related to the principle of collimation oflight by using a photonic crystal.

The exemplary optoelectronic device 700 of FIG. 15A comprises a stack oflayers 702, 703 including an active zone 704 for generatingelectromagnetic radiation, and at least one layer 705 on the mainradiation direction, which comprises a photonic crystal structure 706.

For example, layer 702 is a p-doped GaN layer and layer 703 is ann-doped GaN layer. The layer on the underside 701 can be a metallicmirror layer and/or a carrier layer. The growth direction G goes fromthe top side to the bottom side, or vice versa, and orthogonal to theconnecting surface of the layers.

The photonic crystal structure 706 is formed by nanowires with radius rand height h. The wires form a triangular lattice with lattice constanta. However, other lattice geometries such as square lattice arepossible. The periodicity and thus the lattice constant a of thephotonic crystal structure are such that they are about half thewavelength of the light wavelength to be diffracted. The space betweenthe wires may contain a material, which has a different refractive indexthan the material of the layer 705. For example, layer 705 may be formedof n-doped GaN. Other materials and SiO₂ are also possible.

The layer 702 can be supplied with an extension 702 a, which extendsthrough the layer 703 and reaches into the layer 705 but not into thephotonic crystal structure 706 as shown in the lower view of FIG. 15A.

The photonic crystal structure 706 can have the effect of improving theconcentration of light passing through it. In particular, the photoniccrystal structure 706 can provide a virtual bandgap for a region ofwavelengths that are perpendicular to the direction of growth. Thephotonic crystal structure 706 can block this light. In contrast, lightthat runs along the direction of growth is basically not disturbed bythe photonic crystal structure 706. As shown in the upper view of FIG.15A, the photonic crystal structure 706 in layer 705 can be generatedtwice or even more. The structures 706 are separated from each other bythe distance D.

Alternatively, a single photonic crystal structure 706 can be fabricatedto cover the complete layer 705. In this case, more unit cells of thelattice can be arranged in layer 705, which has a positive effect on theproperties of the photonic crystal structure, which depend on theperiodicity.

In the exemplary device shown in FIG. 15B, layer 702 is not suppliedwith an extension. However, layer 703, which is adjacent to layer 705with crystal structure 706, is provided with a roughened surface, asindicated by projections 703 a, 703 b, 703 c and 703 d. The roughenedsurface can be filled with SiO₂, for example, to fabricate layer 705with photonic crystal structure 706.

In the exemplary device shown in FIG. 15C, the layer 703 is formed witha wigwam surface roughening 703 e. The layer 705 with the photoniccrystal structure 706 may contain SiO₂. The photonic crystal structure706 may be etched into the SiO₂ layer. Air or other material may be inthe space between the photonic crystal structure.

The photonic crystal structure 706 covers the complete layer 703 and isplaced at a distance H from the wigwam surface roughening 703 e of theunderlying layer 703.

Layer 701 is a carrier layer, layer 711 can be a compound layer, layer712 is a mirror layer, especially a silver mirror layer, and layer 713can be a dielectric layer. A mesa dry etch can be performed duringdevice production and after patterning the photonic crystal structure706.

The different photonic decoupling structures create a certain roughnessand surface structures on the surface, depending on their design.Therefore, the surface should be planarized to facilitate a possiblynecessary later transfer. FIGS. 15D to 15F show different aspects ofsurface planarization according to one of several methods of makingphotonic structures on a μ-LED.

Generally, a large number of μ-LEDs are first formed in or on a wafer,then their surface is structured and then, if necessary, separated.Modules of μ-LEDs and other designs are part of this application. It isclear from this that the μ-LEDs come in different designs. The followingsurface treatment is thus independent of the later processing and issuitable for (later isolated) μ-LEDs, μ-LED modules and also pixelatedoptochips with a plurality of μ-LEDs.

According to FIG. 15D, a μ-LED is epitaxially formed with an activelayer in a semiconductor body. The active layer is not shown here. Theμ-LED comprises in its surface area, which is covered by the likewisenot shown carrier, a non-ordered, i.e. random out-coupling structure A,which is formed from the same semiconductor material as thesemiconductor (or parts thereof). The structured surface regiontherefore adjoins the doped layers. The resulting roughness is smoothedagain by applying another transparent material of SiO₂ by means of TEOS(tetraethylorthosilicate) and subsequently planarizing it. Thedecoupling structure improves the decoupling. It is particularlysuitable for the extraction of the light emitted by the active layer.This also reduces optical crosstalk of an adjacent μ-LED with adifferent wavelength.

The other transparent material shows a low refractive index, especiallyless than 1.5, which improves the decoupling from the structured area(higher refractive index). Afterwards the other material is removed byCMP process to form the smooth surface 7 of the structured surface area9. As shown, the removal is either carried out up to the highest areasof the structured area or a surface of the material 5 is generally leftover. In this respect, a gradual transition from a high refractive indexvia the lower refractive index of the material 5 to air results.

In addition to SiO₂ material 5, crown glass with a refractive index ofe.g. 1.46, PMMA with a refractive index of e.g. 1.49 and quartz glasswith a refractive index of e.g. 1.46 can be used. These refractiveindices result at the wavelength 589 nm of the sodium D-line. Arefractive index of silicon dioxide, for example, is 1.458.

FIG. 15E shows a second example of a μ-LED with an output structure. Toimprove light out-coupling, a transparent second material 3 with a highrefractive index is applied to the planar or structured surface of theμ-LED and structured in a suitable way.

For example, a suitable second material 3 with a high refractive indexgreater than 2 is Nb₂O₅ with a refractive index of 2.3. Other usablematerials with a high refractive index are for example zinc sulphidewith a refractive index of for example 2.37, diamond with a refractiveindex of for example 2.42, titanium dioxide with a refractive index offor example 2.52, silicon carbide with a refractive index of for example2.65 and titanium dioxide with a refractive index of for example 3.10.These refractive indices result in particular at the wavelength 589 nmof the sodium D-line. Other materials can also be used.

The structuring of surface area 9 is done, as in FIG. 15D, by creating arandom topology on surface area 9. While according to FIG. 15D therandom topology is created by directly roughening the surface 7 of thesurface region 9 of the semiconductor body comprising a first material1, according to FIG. 15E the random topology is formed by firstdepositing the transparent second material 3 and then roughening it.

After the topology has been created, the rough surface is smoothed byapplying the transparent material 5 described above to the rough surfaceand then planarizing it.

FIG. 15F shows a third example of a μ-LED, but this time with an orderedtopology. This is explained in detail as in the examples in thisapplication by depositing the transparent second material on thesurface. A periodic photonic crystal structure is then introduced intothe second transparent material. Alternatively, photonic properties canbe achieved by non-periodic structures, especially quasi-periodic ordeterministic aperiodic structures.

Alternatively, periodic photonic crystals or non-periodic photonicstructures, in particular quasiperiodic or deterministic aperiodicphotonic structures, can in principle be directly incorporated into thefirst material 1 of the semiconductor body without a second material 3.

After the photonic structure has been formed, the interstitial spacesare filled with a transparent material with a lower refractive index.The transparent third material 5, in particular SiO₂, is planarized,resulting in a smooth and even surface. As shown in FIG. 15F, both thesurface of material 3 and the interstitial material 5 are flat. However,in an alternative embodiment, the transparent third material 5 extendsbeyond the structure of material 3, so that the surface is completelyformed from material 5. In this way, an out-coupling efficiency can beimproved compared to an unmachined surface. A transfer process usingstamp technology remains possible because of the smooth and evensurface.

FIG. 16 shows an example of a proposed method. In a first step S1 anoutput structure A is formed on a surface of a μ-LED. This is done bystructuring the surface. It is possible to structure the semiconductormaterial directly or to provide such a structuring after the depositionof a further material. For this purpose, the surface is covered with aphotomask, which is then exposed to light, thus defining the structures.The surface is structured by various other processes including variousetching steps. In step S2, another transparent material is deposited inthe spaces created after etching. The transparent material covers thepreviously created structure. Subsequently, in step S3 the surface isplanarized by CMP or other suitable processes and removed toapproximately the height of the structures. The structured μ-LED thusproduced can be further processed, separated and transferred.

FIG. 17 shows in a top view and a sectional view a radiation source 6 inthe form of a μ-LED and with a layer 2 arranged in a semiconductorsubstrate 8 of the μ-LED 7, which comprises a photonic structure 4 witha suitable converter material. This is based on the idea of creating aunification of light-shaping and converting structure so that aparticularly space-saving arrangement of the individual elements andthus a particularly small design of an optoelectronic component ispossible. The structured layer 2 with the converter material forms aconverter element 1, whereby the converter material emits convertedradiation into a radiation emission area 3 of the radiation source 6when excited by the excitation radiation emitted by the LED 7.

The structure 4 provided in layer 2 with the converter material isdesigned in such a way that the converted radiation is emittedexclusively as a directed beam in a specific radiation area 3. Accordingto the embodiment shown in FIG. 17, the converted radiation is emittedperpendicular to a plane in which the μ-LED chip with its semiconductorsubstrates is located.

The structured layer 2 shown in FIG. 17 is a two-dimensional photoniccrystal etched into the LED semiconductor substrate above the activelayer of the μ-LED. The individual, here rod-shaped and periodicallyarranged recesses of structure 4 have been filled with the convertermaterial. The layer thickness of structure 4 is at least 500 nm, so thata band gap is created in the crystalline solid-state material, whichcauses a directionality of the converted radiation emitted by converterelement 1. In this example, the recesses are round and arranged in ahexagonal pattern in the center of which a recess is also arranged.However, the recess itself can also take other shapes, for examplehexagonal or square. Round recesses have the advantage that they areeasier to produce. The recesses show the same distance and have the samesize. This circumstance is also due to the application.

For example, the recesses can be of different sizes or have differentspacing. This results in a different periodicity, so that a differentoptical band gap is formed. In a similar embodiment, the recesses canhave a first periodicity in a first direction (i.e. first distance fromeach other and size) and a second periodicity in another, e.g.orthogonal direction. This result in a different band gap in the twospatial directions and a wavelength-dependent selection can be made.With a suitable setting, a full conversion of the incident light ispossible, so that the μ-LED emits converted light substantially parallelto the recesses.

Such a photonic structure can significantly increase directionality andthus efficiency, especially of etendue-limited systems. Due to theprovision of a layer 2 with a corresponding structure 4 and suitableconverter material directly on the surface of the μ-LED 7, the otherwiseadditionally provided optical elements can be dispensed and thus acomparatively small radiation source can be realized by exploiting theinvention. In addition, a particularly efficient radiation source ismade available, since on the one hand, no light is emitted in anunneeded direction that is not perpendicular to the LED chip surface,and on the other hand, all the converted light can be used. Furthermore,modes of the excitation radiation emitted by the μ-LED 7, which areguided in the active zone 9 and have a low extraction efficiency fromthe μ-LED 7, can be efficiently converted.

In addition, FIG. 18 shows the sectional view of a radiation source 6,which is configured as explained in connection with FIG. 17, butadditionally has a filter element 5 applied to the top layer of theradiation source 6 in the form of a filter layer 5, which is opaque toradiation of selected wavelength ranges. The filter layer 5 has thefunction of a color filter.

Such a technical design is particularly suitable for radiation sources6, in which a μ-LED 7 and a converter element 1 are combined in such away that the light emitted by the μ-LED 7 is fully converted. With theaid of a suitably designed filter layer 5, the radiation emitted in theemission range 3 can thus be limited to radiation with a desiredwavelength. Such a filter layer 5 also ensures that the excitationradiation emitted by LED 7, which is not converted into convertedradiation by converter element 1, is prevented from escaping intoemission range 3 by means of filter layer 5 if necessary.

In an alternative embodiment, layer 3 of FIG. 18 assumes an out-couplingfunction in order to appropriately couple out the light formed by thephotonic structure. However, a combination of these two functionalitiesis also possible. In this context, layer 3 can also be structured, forexample roughened, in order to better couple out the light.

FIG. 19 again shows a radiation source 6, which has a μ-LED 7 and aconverter element 1 applied to a semiconductor substrate 8 of the μ-LED7. Converter element 1 comprises a layer 2 with converter material and astructure 4, which is applied to a semiconductor substrate 8 of LED 7.The structured layer 2 is preferably a photonic crystal, aquasi-periodic or deterministically aperiodic photonic structure. Thestructure 4 of layer 2 is filled with suitable converter material.

In contrast to the embodiment explained in FIG. 17, however, thestructured layer 2 is not only arranged in a semiconductor substrate inthe upper area of the radiation source 6, but extends into the activezone 9 of the μ-LED 7. Again, a structured layer 2 with a layerthickness greater than 500 nm is provided, thus creating an optical bandgap. Also in this case, modes of the excitation radiation emitted by theμ-LED 7, which are guided in the active zone 9 and have a low extractionefficiency from the LED, can be efficiently converted.

In addition, FIG. 20 shows a configuration of a radiation source 6,which is configured as shown in FIG. 19 and additionally has a filterelement 5 applied to the top layer of the radiation source 6, which isdesigned in the form of a filter layer serving as a color filter. Suchcolor filters offer the possibility to limit the emission of theconverted radiation into the emission range in case of a full conversionof the excitation radiation emitted by the μ-LED 7 or to selectivelysuppress the emission of unconverted excitation radiation in case of anot complete conversion.

FIGS. 21A and 21B show a μ-display with a photonic structure for theemission of light that preferably emerges vertically from a lightemission surface 21. The device comprises an array 11 having pixels,wherein optically acting nanostructures in the form of a photoniccrystal K are formed over the entire emitting surface of the light exitsurface 21. The array 11 also comprises an array-like arrangement oflight sources, each of which comprises a recombination zone 2, whichlies in a recombination plane 1.

The recombination zones 2 are formed in a first layer of opticallyactive semiconductor material 3 of array 11. The zones 2 can comprisequantum dots, one or more quantum wells or even a simple pn junction. Inorder to obtain more localized recombination regions, it may be intendedto limit recombination to predefined areas by current confinement orother structural measures.

In the layer with the semiconductor material 3, the photonic crystal orphotonic crystal structures K are structured, namely in the form of atwo-dimensional photonic crystal. The photonic crystal K is locatedbetween the recombination zones 2 and the light-emitting surface 21. Thephotonic crystal structures K can be arranged independently of thepositioning of individual pixels, whereby in the example shown one pixelcorresponds to one or three light sources with a recombination zone 2.Three light sources, therefore, so that any color can be produced bysuitable color mixing.

The optically active photonic crystal structures K are filledfree-standing in air or, as shown, with a first filling material 7, inparticular electrically insulating and optically transparent, inparticular SiO₂, with a refractive index which is lower than therefractive index of the semiconductor material 3. The filling material 7preferably also comprises a low absorption coefficient.

In the array 11, both electrical poles of each light source areelectrically connected by means of an optically reflective contact layer5 for the electrical contacting of the light sources. The contactinglayer 5 is located on a side of the optically active semiconductormaterial 3 facing away from the optically active photonic crystalstructures K and is arranged below as shown in FIG. 21B. This type ofcontacting enables very strongly localised recombination zones 2. Forthis purpose, the contacting layer 5 comprises at least two electricallyinsulated areas in order to be able to connect the poles electricallyseparately.

The photonic crystal K can be structured over the entire emittingsurface 21 in such a way that at least approximately only light with apropagation direction perpendicular to the surface 21 can leave thecomponent. If the photonic crystal K is close to the recombination plane1 and the layer thickness of the photonic crystal K is large incomparison to the distance to the recombination zone 2, the opticaldensity of states in the area of light generation is additionallychanged.

This makes it possible to generate a complete bandgap for optical modeswith propagation direction parallel and at a small angle to the surfaceof the, in particular, planar, i.e. in particular flat and/or smooth,pixel-containing array 11. The emission of light with propagationdirection parallel to the emitting surface is then completelysuppressed.

In particular, light can only be generated in a limited emission cone,which is defined by the photonic crystal K. In this case, directionalityis already ensured at the level of light generation, which effectivelyincreases efficiency compared to an angle-selective optical element,since such an element only influences light extraction.

The alignment of the photonic crystal K is independent of thepositioning of the individual pixels, especially in such a way that analignment of the pixel structure to the photonic structure K is notnecessary and processing of an entire wafer surface is possible. It is areasonable embodiment if the device is homogeneous in its opticalproperties over the entire surface of the array 11 or varies onlyslightly so as not to disturb the optical environment of the photoniccrystal K.

FIGS. 22A and 22B show a second proposed optoelectronic device in a planview and in cross-section respectively. In the pixelated array 11, thephotonic crystal K is arranged in a second layer of a material 9, inparticular Nb₂O₅, above a first layer of the optically activesemiconductor material 3, as an alternative to the embodiment shown inFIGS. 21A and 21B. The material 9 thereby has a large optical refractiveindex and it is arranged on the flat and/or smooth surface of thesemiconductor material 3. Preferably, the material 9 also comprises alow absorption and is therefore very transparent. The contacting issimilar to that shown in FIGS. 21A and 21B and allows very localizedrecombination zones 2.

Alternatively, some embodiments may provide that the material is alsoelectrically conductive. This is especially useful if the differentpixels are designed with vertical μ-LED packages and are to be connectedto a common contact.

As shown in FIGS. 21A and 21B, columns are formed from the material 9and the photonic crystal K is in turn formed as a free-standingtwo-dimensional photonic crystal. The space between the columns isfilled with a different material with a lower refractive index than inFIGS. 21A and 21B. A possible filling material is for example SiO₂.

FIGS. 23A and 23B show a third proposed optoelectronic device in a topview and in a cross-section, respectively. The device shown comprises aslight sources an array of vertical μ-LEDs 13 and a two-dimensionalphotonic crystal structure K arranged in an overlying layer, whichextends over the entire emitting surface 21 and is formed from amaterial 9 with a high refractive index. The free space of the structureK is in turn filled with filler material 7 with a lower opticalrefractive index.

The vertical light-emitting diodes 13 have an upper and a lowerelectrical contact along a vertically oriented longitudinal axis, whichis perpendicular to the light-emitting surface 21. The light-emittingdiodes thus comprise an electrical contact on the front side and anelectrical contact on their rear side.

The rear side is the side of the μ-LEDs 13 facing away from the lightemission surface 21, while the front side faces the light emissionsurface 21.

The device comprises an electrically conductive and the generated lightreflecting contacting layer 5 for the electrical contacting of thecontacts on the back of the LEDs 13 The contacting layer 5 is designedin such a way that the individual μ-LEDs can be controlled separately.For the electrical contacting of the contacts on the front of the LEDs13, a third layer is provided, which comprises an electricallyconductive and optically transparent material 17, for example ITO. Anelectrical connection to the corresponding pole of a power source can beestablished via a bonding wire 19.

In and along the recombination level 1, a further, in particularelectrically insulating, filling material 15 can be arranged between thethird layer and the optically reflective contacting layer 5. Thiselectrically separates the μ-LED from each other. In addition to thisstructure shown here, other pixelated components disclosed in thisapplication may also be provided with the structure K. These include,for example, the disclosed antenna structures, the μ-LED in bar form orthe μ-LED modules. Likewise, in all the embodiments shown here,reflective structures may be provided in layer 5 which deflect the lightin the direction of the exit surface. These include the structuressurrounding the actual μ-LED, which are disclosed in this application.

FIGS. 24A and 24B show a fourth version of a μ-display in a top view andcross-section. The μ-display or module device comprises an array ofhorizontal μ-LEDs 13 with respective recombination zones 2 and anoptically effective two-dimensional photonic crystal structure K belowthe total emitting surface 21. The photonic crystal structure K islocated in a layer of a material 9 with a high refractive index, forexample Nb₂O₅. Free spaces are in turn filled with filling material 7,for example silicon dioxide, with a lower optical refractive index.

In the case of the horizontal LEDs 13, both electrical contacts arelocated on the rear of the LEDs 13. Both poles of the LEDs 13 areelectrically connected by means of electrically separated areas of theoptically reflective contact layer 5. In the area of the recombinationlevel 1, a filling material 15, in particular an electrically insulatingone is arranged between the material layer 9 and the contacting layer 5.

The efficiency with respect to light generation is relatively high inthe embodiments according to FIGS. 21A to 24B, since in theseembodiments directionality or directionality of the light is alreadyachieved during light generation, especially if a higher photonic statedensity can be achieved in the area of the recombination zones 2 for theemission of light in the direction perpendicular to the light exitsurface by means of the band structure of the photonic crystal K. Afurther advantage is that the structuring of the photonic crystal K canbe carried out homogeneously over an entire wafer. A certain positioningor orientation of the photonic crystal to the individual pixels or microlight emitting diodes is not necessary. This will significantly reducemanufacturing complexity, especially compared to alternative approacheswhere structures are placed individually over each pixel.

FIGS. 25A and 25B show a fifth proposed optoelectronic device in a topview and cross-section. The device comprises a pixelated array 11 andoptically acting columnar or pillar structures P, in particular withpillars or columns structured over the entire emitting surface 21. Thearray 11 is smooth and flat on its surface.

The pixelized array 11 in this configuration comprises a large number ofsubpixels, each with a light source that includes a respectiverecombination zone 2. The recombination zones 2 of the pixels arelocated in a recombination plane 1 and they are arranged in a firstlayer with optically active semiconductor material 3.

Above this first layer the pillar structures P are formed. One pillar Pis assigned to a light source, so that each Pillar P is located directlyabove the recombination zone 2 of the assigned light source. Alongitudinal axis L of each pillar P runs in particular through thecenter M of the recombination zone 2 of the assigned light source 2. Thepillars P consist of a material 9 with a high refractive index, forexample Nb₂O₅. A filler material 7 with a lower refractive index, suchas silicon dioxide, can be arranged in the spaces between the pillars P.

The pillars P can be arranged above the layer with the light sources, inparticular by additionally applying the pillars P above array 11.Alternatively, the pillars can be etched into the semiconductor material3. For this purpose, the semiconductor material layer must beappropriately high. Since the semiconductor material normally comprisesa high refractive index, material can be etched away in such a way thatthe pillars 9 remain standing. The areas freed up by etching can befilled with material of low refractive index.

The pillars P act like waveguides which guide light upwards in thedirection of the longitudinal axis L, so that the pillars P can cause animproved emission of light in a direction perpendicular to the lightemission surface 21. In addition to the design shown here, theperiodicity of the pillar structures can also be different, for example,the pillars can be located alternately above one μ-LED and between twoadjacent μ-LEDs. This results in a double density of columns. Theperiodicity determines the optical band structure and thus theproperties with regard to light extraction.

In the array 11, both electrical poles of a light source areelectrically connected to the recombination zones 2 by means of areflective contact layer 5. The contacting layer 5 is formed on a sideof the semiconductor material 3 that is turned away from the opticallyactive pillar structures P. The contacting layer 5 can have two separateareas in order to be able to contact electrically the two polesseparately. This type of contacting allows very localized recombinationzones 2.

FIGS. 26A and 26B show a sixth optoelectronic device in a top view andcross-section. The device comprises an array of vertical μ-LEDs 13.Optically active pillar structures P, in particular with pillars orcolumns, are arranged above the array of μ-LEDs 13. The longitudinalaxis L of the pillars P runs at least essentially through the centers ofthe recombination zones 2 of the μ-LEDs 13.

Pillar structures P may be free-standing in air or filled with a firstfilling material 7, in particular electrically insulating and opticallytransparent, above the light-emitting diodes. The filling material 7 maycomprises a lower refractive index than the refractive index of thematerial 9 of the pillars P and/or the semiconductor material 3 of theμ-LEDs 3. The reverse form is also possible, i.e. material 7 has ahigher refractive index than the material of the pillars, but thischanges the light guidance of the pillars.

As already mentioned, the μ-LEDs are vertical micro-light emittingdiodes 13, which comprise one, especially positive, electrical pole ontheir back side facing the reflective contact layer 5 and anotherelectrical pole on the front side facing the pillars P.

The pole at the front of the light sources is electrically connected toan appropriate power supply (not shown) by means of a layer of anelectrically conductive and optically transparent material 17, inparticular ITO, and by means of a contact wire 19. The layer of material17 is placed between the light sources and the pillars 17, as shown.

A second filling material 15 can be arranged in free spaces in the layerof μ-LEDs 13 and thus between the layer with the material 17 and thecontacting layer 5.

Pillar structures P can also be described as micropillar structures ormicropillars, since their dimensions, in particular their cross-section,can at least approximately correspond to the dimensions of the microlight-emitting diodes 13 or the pixels of an array 11.

FIGS. 27A and 27B show a seventh optoelectronic device in a top view andcross-section. In contrast to the variant in FIGS. 26A and 26B, thedevice in FIGS. 27A and 27B comprises an array of horizontalmicro-light-emitting diodes 13, the electrical poles of which arelocated at the rear of the microlight-emitting diodes 13. For electricalcontacting, therefore, both electrical poles of a light source can beelectrically connected via two electrically separated areas of thereflective contacting layer 5. The intermediate layer with the material17 as in the variant with vertical micro light emitting diodes describedabove is therefore not required.

In comparison to the arrangements with the photonic crystal structures Kaccording to FIGS. 21A to 24B, the variants with the pillars P can bemanufactured more easily with standard technologies, since the structuresizes with diameters of up to 1 μm or more are significantly larger. Theprocess requirements are therefore lower and high-resolution lithographycan be sufficient for the manufacture of the pillars.

Pillar structures, in particular pillars or columns, made of theoptically active semiconductor material 3 or a material 9 with arefractive index as high as possible can be precisely structured viaindividual pixels of the array 11 or via vertical micro-light emittingdiodes 13 (FIGS. 26A and 26B) or via horizontal micro-light emittingdiodes 13 (FIGS. 27A and 27B). The individual pixels or micro-lightingdiodes 13 may be smaller than 1 μm in diameter and the pillars may havean aspect ratio height:diameter of at least 3:1. Pillars are preferablyetched directly into the semiconductor material 3, as is possible inFIGS. 25A and 25B and in FIGS. 27A and 27B, because there is no thirdlayer 17 as shown in FIG. 26B, or they are made of another material 9with a high refractive index and preferably low absorption, which isapplied to the surface of the array 11. A possible material with a highrefractive index is for example Nb₂O₅. Pillar structures can befree-standing or filled with a material 7 of low refractive index. Apossible filling material with low refractive index is for example SiO₂.Due to the higher refractive index of the pillars compared to thesurrounding material, the emission parallel to the longitudinal axis ofthe pillars is enhanced compared to other spatial directions. Due to awaveguide effect, light along the longitudinal axis of the pillars isadditionally coupled out more efficiently than light with otherpropagation directions. This improves the directionality of the emittedlight.

FIGS. 28A and 28B show an eighth proposed optoelectronic device in a topview and cross-section. The device comprises an array of μ-LED 13, eachof which is configured with pillar P and thus in column form.

The length of the pillars P can correspond to half a wavelength of theemitted light in the semiconductor material 3 and the recombination zone2 can preferably be located in the center M of a respective pillar andthus in a local maximum of the photonic state density. The aspect ratioheight:diameter of the pillars P can be at least 3:1.

In the arrangement shown, the pillars P can be about 100 nm high andhave a diameter of only about 30 nm. This requires a very finelyresolved structuring technique and can be realized with currentproduction technologies at wafer level with a lot of effort.

Alternatively, the dimensions can be upscaled to simplify manufacture,with the directionality of the emitted light decreasing as the size ofthe pillar structure increases. The length of the pillars P ispreferably a multiple of half the wavelength of the emitted light in thesemiconductor material, and the respective recombination zone 2 can beat a maximum of the photonic state density.

Due to the pillar structuring of the μ-LED 13, the emission parallel tothe longitudinal axis of the pillars P is effectively amplified by thehigher photonic state density. Due to a waveguide effect, light with adirection of propagation along the longitudinal axis of the pillars P isadditionally coupled out more efficiently than light with otherdirections of propagation. The space between the pillars P is filledwith a material 7, which preferably comprises a very low absorptioncoefficient and a lower refractive index than the semiconductor material3. A possible filling material with a low refractive index is forexample SiO₂.

In this arrangement of micro-lighting diodes 13, in particular verticalmicro-lighting diodes 13 formed as pillars P or columns, a first pole,in particular a positive pole is electrically connected by means of areflective contacting layer 5 for contacting recombination zones 2arranged in a recombination plane 1. The contacting layer 5 is formed atthe lower, first longitudinal ends of the μ-LEDs 13.

The respective other, in particular negative, second pole iselectrically connected to a third layer of a conductive transparentmaterial 17, in particular ITO, and connected by means of a bonding wire19 for example to the corresponding pole of a power supply.

According to this arrangement, the third layer is formed in and alongthe recombination plane 1 in the longitudinal centers of the μ-LEDs 13,which are shaped as pillars P or columns.

FIGS. 29A and 29B show a ninth optoelectronic device in a top view andcross-section. In contrast to the variant in FIGS. 28A and 28B, thedevice in FIGS. 29A and 29B comprises vertical μ-LEDs in the form ofpillars P.

The electrical contact at the bottom, in particular the p-contact, isestablished via the bottom of the pillars P and in particular bycontacting the contact layer 5. The electrical contact at the top,especially the n-contact, is on the upper side of the pillars P. Thecontact is established via an upper layer of optically transparent andelectrically conductive material 17. The upper layer extends over thepillars P and the first filling material 7, with which the free spacesbetween the pillars P are filled. A possible material 17 for the upperlayer is ITO (indium tin oxide), for example. A connection to a powersupply can be established via the bonding wire 19.

The electrical contacting of the light-emitting diodes in the pillars Penables very strongly localized recombination zones 2, whereby the uppercontact, in particular an n-contact, can be formed at the level of therecombination zones 2 or on the upper side of the pillars P. Each pillarP generates an individual pixel.

The emission of light parallel to the longitudinal axis of μ-LEDs 13 inthe form of pillars as shown in FIGS. 28A to 29B is increased. Thisimproves the directionality of the emitted light compared toconventional micro-light emitting diodes with small aspect ratio.Compared to an arrangement according to FIGS. 25A to 27B, the process oflight generation can be influenced much more strongly by an arrangementaccording to FIGS. 28A to 29B, thus achieving high directionality andefficiency.

FIG. 30 shows a cross-sectional view of another optoelectronic device inwhich a two-dimensional photonic crystal K is arranged over a layer withan array of light sources with recombination zones 2. The photoniccrystal K is thereby arranged so close to the recombination zones 2 thatthe photonic crystal K changes an optical state density present in theregion of the recombination zones 2, in particular in such a way that aband gap is generated for at least one optical mode with a direction ofpropagation parallel and/or at a small angle to the light exit surface21 and/or the state density is increased for at least one optical modewith a direction of propagation perpendicular to the light exit surface21.

This can be achieved in particular by the fact that the height H of thephotonic crystal K is at least 300 to 500 nm, preferably up to 1 μm. Theheight H of the photonic crystal may depend on the high refractive indexmaterial of the photonic crystal.

Furthermore, a distance A between the center M of the recombinationzones 2 and the bottom of the photonic crystal K is at most 1 μm andpreferably a few 10 to a few hundred nm.

All the described configurations with a photonic crystal K aretwo-dimensional photonic crystals, which exhibit a periodic variation ofthe optical refractive index in two spatial directions perpendicular toeach other and parallel to the light-emitting surface. Furthermore, itis preferably a pillar structure comprising an array of pillars P orcolumns, the longitudinal axis L of the pillars P being perpendicular tothe light-emitting surface 21.

FIG. 31 shows an optoelectronic device 1 with a photonic structure foremitting polarized light. The component 1 comprises an emitter unit 2,which has a light-emitting surface 3 and on which a polarizing element 4in the form of a polarizing layer with a three-dimensional photonicstructure is applied. With the help of photonic structures forpolarization of electromagnetic radiation, it is especially possible totake special pictures and show them on suitable displays. According tothe embodiment shown in FIG. 31, emitter unit 2 is a μ-LED 5, whichemits light in the visible or possibly also in the ultravioletwavelength range. The light emitted by the μ-LED 5 is guided into thethree-dimensional photonic structure and here it is polarized in acertain direction of oscillation depending on the design anddimensioning of the structure. Depending on the design of thethree-dimensional photonic structure, either circular or linearpolarization can be used. The light emitted in this way thereforecomprises a specific polarization, which is predetermined by thephotonic structure.

If the three-dimensional photonic structure of polarization element 4has spiral structure elements 6 as shown in FIG. 32, a circularpolarization occurs. If, on the other hand, the structural elements ofthe three-dimensional photonic structure are rod-shaped, in particularin the form of so-called nanorods, this causes a linear polarization ofthe radiation guided through the three-dimensional photonic structure.

The optoelectronic device 1 shown in FIG. 31 is manufactured by thetwo-photon lithography process, the glancing angle deposition process,laser interference lithography or by holographic patterning. It shouldbe noted that the spiral-shaped features 6 shown in FIG. 32 have beenfabricated using the glancing angle deposition technique.

The illustration in FIG. 31 shows only a single optoelectroniccomponent. However, a large number of these components can bemanufactured together and provided as an array or μ-LED module, as shownin FIGS. 187, 189 to 192, for example. In this way, different componentscan be interconnected, but with complementary properties. Thus,components 1 or also arrays or μ-LED modules are combined for imaging,which have different polarization and/or transmission properties.

The radiation generated by several illumination units, each withcomplementary properties, polarized in different directions ofoscillation, is projected onto a display or screen by means of commonoptics disclosed therein.

With the three-dimensional photonic structure arranged on the surface orlight-emitting surface 3 of an LED chip as shown in FIG. 31, which formsa polarization element 4, it is possible to generate light withfundamentally different properties, in particular with definedpolarization, than is possible with the currently known LEDs. Theadvantage is that due to the provision of a three-dimensional photonicstructure on the chip surface, no additional optical components, such asa classical polarization filter, are required. This is particularlyuseful in the area of μ-LEDs, since such photonic structures are easierto produce by means of lithographic processes than by positioning andattaching separate polarization filters. The illumination unit cantherefore be made comparatively small. Due to the structuring directlyon the semiconductor chip of the LED 5, such an optoelectronic component1 is also more energy-efficient than the known components in which thepolarization is subsequently selected. Any photon that does not passthrough the three-dimensional photonic structure due to its propertiesremains in the μ-LED chip and can be re-emitted by a reabsorptionprocess.

FIG. 33 shows an illumination unit or an optoelectronic component 1 withan emitter unit 2, which comprises a light-emitting surface 3 on which apolarizing element 4 with a three-dimensional photonic structure thathas wavelength-selective properties is applied. The photonic structurein this case is a three-dimensional photonic crystal. Alternatively,several two-dimensional photonic crystals can be arranged in layers oneabove the other.

The three-dimensional photonic structure is designed to havewavelength-specific transmittance and polarization properties. Thismeans that the transmittance and polarization properties of thethree-dimensional photonic structure vary depending on the wavelength ofthe incident radiation.

Component 1 shown in FIG. 33 has an emitter unit, which in turn has aμ-LED 5. A converter element 7 with a layer of converter material isalso provided. The converter material emits a converted radiation 9 dueto excitation by the excitation radiation 8 emitted by the LED 5, whichcomprises a different wavelength than the excitation radiation 8.

If both unconverted excitation radiation 8 and converted radiation 9impinge on the three-dimensional photonic structure, these radiationsare influenced in different ways depending on their wavelength withrespect to transmission and polarization. As shown in FIG. 33, theconverted radiation 9 is coupled out perpendicular to the surface of theLED chip, while the excitation radiation 8 is deflected laterally.

Such lighting units can be used in a preferred way in components inwhich radiation with different wavelengths is generated, wherebydifferent functions can be implemented with a combination of μ-LEDs andconverter elements. Depending on the design of the three-dimensionalphotonic structure and the wavelength of the excitation radiation 8emitted by each LED, it is possible to achieve complete suppression ofthe excitation radiation 8, while the converted radiation 9 passesthrough the three-dimensional photonic structure. It is also conceivablethat the excitation radiation 8 is deflected while the convertedradiation 9 is coupled out perpendicular to the chip surface, as shownin FIG. 33. Of course, the mechanism can also be reversed. Furthermore,it is also conceivable to polarize the converted radiation 9 in aspecial way, while the excitation radiation 8 emerges unchanged via thechip surface. Here too, the mechanism can be reversed.

The variant of an illumination unit shown in FIG. 34 comprises anemitter unit, here again in the form of a μ-LED 15, and athree-dimensional photonic structure 11, for example a spiral-shapedphotonic structure 11. Converter material 13 is filled into structure11.

The optoelectronic component 11 shown in FIG. 35 comprises at least oneμ-LED 13, which is designed to emit electromagnetic radiation 19, suchas visible or infrared light of one wavelength, via a light emissionsurface 15. A photonic structure 17 is provided for beam-shaping of theelectromagnetic radiation before it exits via the light exit surface 15.The photonic structure 17 shapes the electromagnetic radiation 19 insuch a way that the electromagnetic radiation 19 comprises a definedcharacteristic 23 (Far-field characteristics).

In particular, the photonic structure 17 of the illumination unit 11 ofFIG. 35 is a one-dimensional photonic crystal 25, which in the variantshown extends to the light-emitting surface 15. The front side of thephotonic crystal 25 thus forms the light-emitting surface 15. Theone-dimensional photonic crystal 25 exhibits a periodic variation of theoptical refractive index along a first direction R1.

The crystal 25 or the periodic variation are adjusted to beam theelectromagnetic radiation emitted by a light source (not shown) of theμ-LED. Especially a light propagation along the first direction R1 isblocked. As a result, the emitted radiation 19 in far-field 21 comprisesonly a slight extension along the first direction R1. A characteristicfeature of electromagnetic radiation 19 in far-field 21 is thereforethat it forms a narrow strip 27. The electromagnetic radiation 19 istherefore collimated with respect to the first direction 19.

The light source is a μ-LED. This is typically a Lambertian radiator. Byusing the photonic structure 17 and the resulting beam-shaping adirected, collimated electromagnetic radiation 19 can be generated.

As FIG. 35 schematically shows, the emitted electromagnetic radiation 19leaves the μ-LED 13 in the form of a light cone that substantially fansout along a second direction R2. The central axis of the light coneextends along a main radiation direction H, which is perpendicular tothe light exit surface 15. Not shown is a collimating, optional opticalsystem arranged downstream of the light exit surface 15 when viewed inthe main radiation direction H. By means of the optics, theelectromagnetic radiation 19 can be collimated in the second spatialdirection R2, which is orthogonal to the first spatial direction R1. Theelectromagnetic radiation 19 can thus be collimated in the far field 21with respect to the two directions R1, R2. A luminous point is created.This luminous point is particularly favourable for displays as mentionedat the beginning, because the beam is strongly collimated in bothdirections in space.

An optoelectronic component 11 as shown in FIG. 35 is particularly wellsuited for use in an optical scanner. Here, the illumination device 11can be used especially for line scan applications due to the stripe-likelight image in far field 21.

In the optoelectronic device 11 shown in FIG. 36, a one-dimensionalphotonic crystal 25 is formed on the upper side of an emitter unit 13 a.The front face of the crystal 25 forms the light-emitting surface 15 forelectromagnetic radiation generated by an unrepresented optoelectroniclight source, for example an LED or μ-LED, which is emitted through thephotonic crystal 25 via the light-emitting surface 25.

In contrast to the variant shown in FIG. 35, the main direction ofradiation H of the electromagnetic radiation 19 of the lighting unit ofFIG. 36 is at an angle α to the normal N of the light-emitting surface15. The angle α is not equal to zero degrees. For example, the angle αcan be in the range between 30 and 60 degrees. This is achieved by thefact that the one-dimensional photonic crystal 25 comprises aperiodically repeating sequence of two materials 31, 33 with differentoptical refractive indices extending in a first direction R1. Thematerials 31, 33 have a parallelogram-like cross-section and abuttinginterfaces of the materials 31, 33 do not run orthogonally but areinclined to the light-emitting surface 15, as shown schematically inFIG. 36.

Such a structure can be formed, for example, by etching trenches 29running parallel to each other at an angle to the light emission surface15 into the substrate 31 having the light emission surface 15. Thetrenches 29 can be filled with a material 33, which comprises adifferent optical refractive index than the substrate material 33, whichhas been etched away. The angle α may depend on the inclination of thetrenches 29 to the light-emitting surface 15. The width of the trenches29 and the width of any substrate material 31 remaining between twotrenches 29 influences the wavelengths at which the photonic crystal 25can be affected. Typically, the width of the trenches 29 and the widthof the substrate material 33 remaining between two trenches, and thusalso the periodicity of the photonic crystal structure 25, are adaptedto the wavelength of the electromagnetic radiation provided by the lightsource or a converter material located between the light source and thephotonic crystal.

Using the one-dimensional photonic crystal 25, component 11 of FIG. 36can in turn generate a light strip 27 in the far field 21, as describedin relation to FIG. 35. In contrast to the variant in FIG. 35, the mainradiation direction H in the variant in FIG. 36 is tilted by the angle αrelative to the normal N. By means of a downstream collimating optic,the strip 27 can be brought into a point-like or circular structure inthe far field 21.

The variant shown in FIG. 37 comprises a linear or array arrangement ofseveral optoelectronic components 11 of FIG. 36, the light beams 19emitted by the individual components 11 having the same main radiationdirection H. The light beams 19 can also be collimated by an additionalcollimating optic 35, in particular a lens, in a second direction,which, in the representation of FIG. 37, is perpendicular to the imageplane. This results in a point or circular image of the emittedradiation 19 in the far field behind the lens 35.

The use of a photonic crystal in an illumination device 11 as shown inFIGS. 36 and 37 results in an effectively higher resolution for aline-array arrangement of illumination devices 11 as shown in FIG. 37.μ-display or modules having such features allow very directionalradiation, so that the pixel sharpness is very high. This means that thecontrast remains very high even with adjacent pixels and opticalcrosstalk is reduced. In addition, smaller beam cross-sections can berealized, especially in the far field, downstream of optics 35. Sincecollimation in the first direction R1 (cf. FIG. 36) is already achievedby the photonic crystals 25 integrated in the illumination devices 11,optics 35 and possibly further, subsequent optics can be made morecompact.

In the variant of FIG. 38, the optoelectronic component or lighting unit11 comprises a photonic structure 17, which is a two-dimensionalphotonic crystal 37, whose front side forms the light-emitting surface15. Viewed from the light exit surface 15, at least one optoelectroniclight source, optionally with converter material, is arranged behind thephotonic crystal 37. The photonic crystal 37 is designed to shape theelectromagnetic radiation 19 emitted via the light exit surface in sucha way that it produces a defined, discrete pattern 39 in the far field21. In the example shown, the pattern 39 consists of several distributedlight spots 41, although other patterns are also possible. Inparticular, the photonic crystal can be formed to produce only onecentral pixel. This structure is particularly useful for displays.

The illumination device 11 in FIG. 38 is suitable for use in a surfacetopography detection system 43, for example, as shown in the blockdiagram in FIG. 39. In addition to the illumination device 11, thesystem 43 includes a detection unit 45 with a camera 47, which isdesigned to detect the pattern 39 when it illuminates an object (notshown).

Furthermore, an analysis device 49 is provided which is designed todetect a distortion of the pattern 39 in relation to a given referencepattern. The reference pattern can, for example, be determined from thedetection of pattern 39 when it is projected onto a flat surface. Theanalyser 49 is also adapted to determine a shape and/or a structure ofthe object illuminated by the pattern 39 in the far field 39 dependingon the detected distortion of the pattern 39. By means of the system 43,face recognition can thus be realized, for example. In the case ofapplications in the Augmented Reality area, some pixels can be formedwith a crystal such as the one shown in FIG. 38 in order to detect thereflection on the eye a direction of vision or its change. This allows auser to follow and superimpose information into the field of view forsharp vision.

In the variant shown in FIG. 39, downstream optics for patterngeneration can be dispensed with, since pattern 39 can already begenerated using photonic crystal 37. The lighting device 11 as shown inFIG. 38 and the associated system 43 as shown in FIG. 39 can thereforebe implemented in a particularly compact form.

In the following, various devices and arrangements as well as methodsfor manufacturing, processing and operating as items are again listed asan example. The following items present different aspects andimplementations of the proposed principles and concepts, which can becombined in various ways. Such combinations are not limited to thoselisted below:

565. μ-LED, comprising:

-   -   a layer stack of a p-doped layer;    -   an n-doped layer;    -   an active region located between the p-doped and n-doped layer;

wherein the layer stack rises above a major surface and the activeregion is located above a center of the layer stack as viewed from themajor surface, wherein the layer stack has a reducing diameter from themajor surface;

a reflective layer over a surface of the layer stack.

566. μ-LED according to item 565, in which the stack of layers comprisethe shape of a hemisphere or a paraboloid or an ellipsoid.

567. μ-LED according to any of the preceding items, in which areas ofthe active layer adjacent to the reflective layer comprise an increasedbandgap.

568. μ-LED according to any of the preceding items, in which areas ofthe active layer adjacent to the reflective layer exhibit quantum wellintermixing.

569. μ-LED according to any of the preceding items, in which thereflective layer comprises a dielectric between the active region andthe layer of the layer stack adjacent to the surface region.

570. μ-LED arrangement for generating a pixel of a display, comprising

-   -   a flat carrier substrate; and    -   at least one μ-LED, which is arranged on a mounting side of the        carrier substrate

wherein the μ-LED is adapted to emit light transverse to a carriersubstrate plane in a direction away from the carrier substrate;

-   -   a flat reflector element;

wherein the reflector element is spatially arranged on the assembly siderelative to the at least one μ-LED and is configured to reflect lightemitted by the at least one μ-LED in the direction of the carriersubstrate;

wherein the carrier substrate is at least partially transparent so thatlight reflected from the reflector element propagates through thecarrier substrate and emerges at a display side of the carrier substrateopposite the mounting side.

571. μ-LED arrangement according to item 570, wherein a diffuser layeris provided and/or a reflector material has diffuser particles forscattering the light reflected by the at least one μ-LED on the side ofthe reflector element directed towards the at least one μ-LED.

572. μ-LED arrangement according to item 571, wherein the diffuser layerand/or the diffuser particles comprise Al₂O₂ and/or TiO₂.

573. μ-LED arrangement according to any of the preceding items, whereinthe reflector element surrounds the at least one μ-LED in a circular,polygonal or parabolic shape.

574. μ-LED arrangement according to any of the preceding items, whereinthe reflector element forms an electrical contact of the at least oneμ-LED.

575. μ-LED arrangement according to any of the preceding items, whereinthe reflector element is configured and shaped such that at least 90% ofthe light emitted by the at least one μ-LED is incident on the mountingside of the carrier substrate at an angle between 45 and 90 degreesrelative to the carrier substrate plane.

576. μ-LED arrangement according to any of the preceding items, in whichthe at least one μ-LED comprises three μ-LEDs surrounded by thereflector element

577. μ-LED arrangement according to item 576, in which the at leastthree μ-LEDs have a contact area on the side facing the reflectorelement, which is covered with a transparent cover layer for commonelectrical contact.

578. μ-LED array according to any of the preceding items, wherein thesupporting substrate comprises polyamide, a transparent plastic, resinor glass.

579. μ-LED arrangement according to any of the preceding items, whereinthe reflector element is formed as a reflective layer of the at leastone μ-LED.

580. μ-LED arrangement according to any of the preceding items, whereina passivation layer is additionally provided for attenuating oreliminating reflections of the light at mesa edges of the at least oneμ-LED.

581. μ-LED arrangement according to any of the preceding items, whereina light absorbing coating is provided on the assembly side and/ordisplay side of the carrier substrate outside the reflector element.

582. μ-LED arrangement according to any of the preceding items, whereinthe display side of the supporting substrate has an uneven and/orroughened structure.

583. μ-LED arrangement according to any of the preceding items, whereina color filter element is arranged on the display side of the carriersubstrate opposite the reflector element;

wherein the color filter element allows a primary color spectrum of theat least one μ-LED to pass and attenuates deviating color spectra.

584a. μ-LED arrangement according to any of the preceding items, inwhich a light-shaping structure, in particular a photonic structure withfeatures after one of the following objects is incorporated in thecarrier substrate, which first and second regions with differentrefractive indexes are incorporated.

584b. μ-LED arrangement according to any of the preceding items, inwhich a light-shaping and/or light-converting structure having first andsecond areas is arranged on the display side of the carrier substrate.

585. μ-LED arrangement according to item 583 or 584, where first areascomprise a converter material.

586. μ-LED arrangement according to any of the preceding items,comprising a converter material surrounding the at least one μ-LED andfilling the space between μ-LED and reflector material.

587. μ-LED arrangement according to any of the preceding items,comprising a converter material on the display side of the supportingsubstrate.

588. Optical display comprising a plurality of pixel elements eachaccording to any of the preceding items.

589. A method for producing an optical pixel element, comprising thesteps of

-   -   fixing of at least one μ-LED on an assembly side of a flat        carrier substrate;    -   creating a reflector element;

wherein the reflector element is formed as a light-reflecting layer onthe at least one μ-LED so that light emitted from the at least one μ-LEDis reflected towards the carrier substrate.

590. Photonic structure on an optoelectronic device, in particular aμ-LED, comprising

a set of layers including an active zone for generating electromagneticradiation forming the optoelectronic device, and at least one layer on amain radiation surface having a photonic crystal structure.

591. Photonic structure on an optoelectronic device according to item590, the layers of the set of layers and the at least one layer havingthe photonic crystal structure are arranged one upon another along agrowth direction of the layers, and wherein the photonic crystalstructure comprise a periodicity in a plane perpendicular to the growthdirection.

592. Photonic structure on an optoelectronic device according to item590, in which the photonic crystal structure has first and secondregions of different refractive index.

593. Photonic structure on an optoelectronic device according to any ofthe preceding items, wherein the photonic structure has a firstperiodicity in a first direction and a second periodicity in a seconddirection.

594. Photonic structure on an optoelectronic device as defined in item593, in which the first and second periodicity are the same.

595. Photonic structure on an optoelectronic device according to any ofthe preceding items, in which the photonic crystal structure extends atleast partially into one of the layers of the set of layers.

596. Photonic structure on an optoelectronic device according to any ofthe preceding items, the periodicity corresponding to about half aspecific wavelength, the wavelength corresponding to the wavelength ofelectromagnetic radiation to be diffracted by the photonic crystalstructure.

597. Photonic structure on an optoelectronic device according to any ofthe preceding items, wherein the layer having the photonic crystalstructure is a dielectric layer containing or consisting of, forexample, silicon dioxide, SiO₂, and/or wherein the space within thephotonic crystal structure is filled with or consists of a secondmaterial having a refractive index different from the refractive indexof a first material forming the photonic crystal structure.

598. Photonic structure on an optoelectronic device according to any ofthe preceding items, wherein a lower surface of the layer having thephotonic crystal structure is disposed on an upper surface of the set oflayers.

599. Photonic structure on an optoelectronic device according to item598, wherein a portion of at least one layer of the set of layersprotrudes into the layer with the photonic crystal structure.

600. Photonic structure on an optoelectronic device according to item597 or 599, wherein the upper surface of the set of layers is providedwith a surface roughening, for example, a wigwam surface roughening.

601. Photonic structure on an optoelectronic device after any of theforegoing, wherein the photonic crystal structure is located at adistance from the upper surface of the set of layers.

602. Photonic structure on an optoelectronic device according to any ofthe preceding items, further comprising a mirror layer disposed on thelayer having the photonic crystal structure.

603. Photonic structure on an optoelectronic device according to any ofthe preceding items, further comprising a metal mirror layer, with theset of semiconductor layers disposed between the metal mirror layer andthe layer containing the photonic crystal structure.

604. Photonic structure on an optoelectronic device according to any ofthe preceding items, wherein the optoelectronic device is a μ-LED.

605. Optoelectronic device comprising:

at least one optoelectronic light emitting device, for example a μ-LED,wherein said optoelectronic light emitting device is configured to emitlight through at least one light emitting surface of said optoelectroniclight emitting device,

at least one photonic crystal structure, said photonic crystal structurebeing disposed between the light-emitting surface of said optoelectroniclight-emitting device and a light-emitting surface of saidoptoelectronic device.

606. Method for producing an optoelectronic device, in particularaccording to any of the preceding items, comprising method:

-   -   growing of a set of layers including an active zone for the        generation of electromagnetic radiation,    -   growing at least one layer having a photonic crystal structure        on the upper side of the set of layers,

optionally providing a mirror layer over the layer with the photoniccrystal structure,

optionally providing a mirror layer under the set of layers with theactive zone,

optionally executing an etching process, such as a Mesa dry etchingprocess.

607. Method for producing a μ-LED comprising a

creating of an out-coupling structure in a surface region of asemiconductor body providing the active layer of the μ-LED by means of

structuring of the surface area; and

planarizing the structured surface area to obtain a planarized surfaceof the surface area.

608. Method according to item 607, wherein the step of structuring thesurface area comprises at least one of the following steps:

-   -   generating of a random topology at the surface area;    -   roughening the surface of the surface region of the        semiconductor body comprising a first material;    -   applying, in particular layer-by-layer applying of a transparent        second material having a high refractive index, in particular        greater than 2, to the surface region and roughening of the        second material;

creating an ordered topology on the surface area;

applying, in particular layer-by-layer applying of a transparent secondmaterial having a high refractive index, in particular greater than 2,to the surface region and structuring of periodic photonic structures ornon-periodic photonic structures, in particular quasi-periodic ordeterministic aperiodic photonic structures, into the second material.

609. Method according to item 608, characterised in that

the transparent second material with the high refractive index Nb₂O₅.

610. Method according to any of the preceding items, in which the stepof planarizing comprises:

applying, in particular layer by layer, a transparent third material oflow refractive index, in particular less than 1.5, to the structuredsurface region; and

optionally thinning the applied transparent third material of lowrefractive index until the surface of the structured surface regionterminates flat and/or smooth with highest elevations in the firstmaterial of the semiconductor body or in the second material of highrefractive index.

611. Method according to item 610, in which the transparent thirdmaterial having a low refractive index SiO₂, and is applied inparticular by means of TEOS (tetraethylorthosilicate).

612. μ-LED comprising an out-coupling structure in a surface region of asemiconductor body providing the μ-LED in which the surface area isplanarized so that a smooth surface area is created.

613. μ-LED according to item 612, characterised in that the smoothsurface region comprises a roughness in the range of less than 20nanometres, in particular less than 1 nanometre, as mean roughnessvalue.

614. μ-LED to any of the preceding items, wherein the out-couplingstructure comprises a transparent third material with a low refractiveindex, in particular SiO₂, on a roughened first material of thesemiconductor of the device.

615. μ-LED according to any of the preceding items, in which the outputcoupling structure comprises a transparent third material of lowrefractive index, in particular SiO₂, on a roughened transparent secondmaterial of high refractive index, in particular Nb₂O₅, the secondmaterial being attached to a first material of the semiconductor of thedevice.

616. μ-LED according to any of the preceding items, in which the outputstructure comprises a transparent third material of low refractiveindex, in particular SiO₂, on a transparent second material of highrefractive index, the second material being attached to a first materialof the semiconductor of the device and comprising periodic photoniccrystals or non-periodic photonic structures, in particularquasi-periodic or deterministic aperiodic photonic structures.

617. Converter element for an optoelectronic component, which has atleast one layer comprising a converter material which, when excited byan incident excitation radiation, emits a converted radiation into anemission region,

characterized in that the layer has at least in some areas a structureon which the converter material is arranged at least in sections andwhich is configured in such a way that the radiation is emitted as adirected beam of rays into the emission area.

618. Converter element according to item 617, characterised in that thestructure is quasi-periodic or deterministically aperiodic.

619. Converter element according to item 617 or 618,

characterised in that the layer comprises at least one photonic crystal,a quasi-periodic photonic structure or a deterministically aperiodicphotonic structure.

620. Converter element according to any of the preceding items,characterised in that the structure comprises at least one recess inwhich the converter material is located.

621. Converter element according to any of the preceding items,characterised in that the layer comprises an optical band gap.

622. Converter element according to any of the preceding items,characterized in that the structure comprises an average thickness of atleast 500 nm.

623. Converter element according to any of the preceding items,characterized in that the layer with the structure is configured suchthat the directed beam of rays is emitted perpendicularly to a plane inwhich the layer is arranged.

624. Converter element according to any of the preceding items,characterized in that an optical filter element is arranged at least onone side of the layer.

625. Light-shaping structure for an optoelectronic device comprising atleast one layer with a converter material which, when excited by anincident excitation radiation, emits a converted radiation into anemission region

characterized in that the layer has at least in some areas a structureon which the converter material is arranged at least in sections andwhich is configured in such a way that the radiation is emitted as adirected beam of rays into the emission area.

626. Light-shaping structure according to item 625,

characterised in that the structure is quasi-periodic ordeterministically aperiodic.

627. Light-shaping structure according to item 625 or 626,

characterised in that the layer comprises at least one photonic crystal,a quasi-periodic photonic structure or a deterministically aperiodicphotonic structure.

628. Light-shaping structure according to any of the preceding items,

characterised in that the structure comprises at least one recess inwhich the converter material is located.

629. Light-shaping structure according to any of the preceding items,

characterised in that the layer comprises an optical band gap.

630. Light-shaping structure according to any of the preceding items,

characterized in that the structure comprises an average thickness of atleast 500 nm.

631. Light-shaping structure according to any of the preceding items,

characterized in that the layer with the structure is configured suchthat the directed beam of rays is emitted perpendicularly to a plane inwhich the layer is arranged.

632. Light-shaping structure according to any of the preceding items,

characterized in that an optical filter element is arranged at least onone side of the layer.

633. μ-LED arrangement comprising a μ-LED and a converter elementaccording to any of the preceding items, wherein the μ-LED is adapted toradiate an excitation radiation into the converter element, and whereinthe converter element comprises at least one layer comprising aconverter material.

634. μ-LED arrangement comprising a μ-LED and having a light-shapingstructure according to any of the preceding items, wherein the μ-LED isadapted to irradiate an excitation radiation into the light-shapingstructure, and wherein the light-shaping structure comprises at leastone layer comprising a converter material.

635. μ-LED arrangement according to item 633 or 634,

characterized in that the layer is part of a semiconductor substrate ofthe μ-LED.

636. μ-LED arrangement according to any of the items 633 to 635,characterized in that the structure of the converter element orlight-shaping structure is formed in the semiconductor substrate of theμ-LED.

637. μ-LED arrangement according to any of the items 633 to 636,characterized in that the structure with the converter material isconfigured in such a way that the converted radiation is emitted intothe emission region perpendicular to a plane in which the semiconductorsubstrate is arranged.

638. μ-LED arrangement according to any of the items 633 to 637,characterised in that the structure of the converter element orlight-shaping structure is at least partially disposed in an activelayer of the μ-LED.

639. Method for producing a μ-LED arrangement according to any of theitems 633 to 638,

characterized in that the structure of the converter element or thelight-shaping structure is formed by at least one etching step in asemiconductor substrate of the μ-LED.

640. Method according to item 639,

characterised in that the structure of the converter element orlight-shaping structure is at least partially filled with the convertermaterial.

641. Optoelectronic device or μ-LED array, comprising:

an arrangement comprising a plurality of μ-LEDs for generating lightemerging from a light exit surface from the optoelectronic device, and

at least one photonic structure arranged between the light-emittingsurface and the plurality of μ-LEDs.

642. Optoelectronic device according to item 641, in which the photonicstructure is configured for beam-shaping of the light generated by theμ-LEDs, in particular in such a way that the light emerges at leastsubstantially perpendicularly from the light exit surface.

643. Optoelectronic device according to any of the preceding items, inwhich the photonic structure comprises a photonic crystal.

644. Optoelectronic device according to any of the preceding items, inwhich

the arrangement is an array in which the μ-LEDs represent a plurality ofpixels and are arranged in a layer, and in that a photonic structure isarranged or formed in the layer.

645. Optoelectronic device according to any of the preceding items,characterized in that the arrangement is an array in which the μ-LEDsrepresent a plurality of pixels arranged in a first layer and in that aphotonic crystal is arranged in a further, second layer, the secondlayer being located between the first layer and the light-emittingsurface.

646. Optoelectronic device according to any of the preceding items,characterized in that

the arrangement comprises a plurality of μ-LEDs arranged in a firstlayer, and that a photonic crystal is arranged in the further, secondlayer, the second layer being located between the first layer and thelight-emitting surface.

647. Optoelectronic device according to any of the preceding items,characterized in that

each of the μ-LEDs comprises a recombination zone and the photonicstructure is located so close to the recombination zones that thephotonic structure changes an optical state density present in theregion of the recombination zones, in particular in such a way that aband gap is generated for at least one optical mode with a direction ofpropagation parallel and/or at a small angle to the light exit surface.

648. Optoelectronic device according to any of the preceding items,characterized in that

the photonic structure is arranged in relation to a plane parallel tothe light-emitting surface independently of the positioning of the lightpoints, and/or

the photonic structure is a two-dimensional photonic crystal, whichexhibits a periodic variation of the optical refractive index in twospatial directions perpendicular to each other and spanning the plane.

649. Optoelectronic device according to any of the preceding items,characterized in that

the photonic structure comprises a plurality of pillar structuresextending at least partially between the light-emitting surface and theplurality of μ-LEDs, wherein one pillar is associated with each μ-LEDand is aligned with the light-emitting surface when viewed in adirection perpendicular to the light-emitting surface.

650. Optoelectronic device according to item 649, characterised in that

the device is an array in which the μ-LEDs represent a plurality ofpixels arranged in a first layer and in that the pixels are arranged ina further, second layer, the second layer being located between thefirst layer and the light-emitting surface.

651. Optoelectronic device according to item 649, characterised in that

the device comprises a plurality of μ-LEDs, arranged in a first layer,and that the pillars are arranged or formed in a further, second layer,the second layer being located between the first layer and thelight-emitting surface.

652. Optoelectronic device according to item 649, characterised in that

the arrangement is an array in which the μ-LEDs represent a plurality ofpixels, one pixel being formed by each pillar.

653. Method for producing an optoelectronic device,

in particular a device according to any of the preceding items, whereinan arrangement comprising a plurality of μ-LEDs is provided or made forgenerating light emerging from a light exit surface from theoptoelectronic device, and

at least one photonic structure is arranged between the light-emittingsurface and the plurality of μ-LEDs.

654. μ-LED arrangement having at least one μ-LED which emits radiationvia a light-emitting surface, and having a polarization element whichadjoins the light-emitting surface at least in sections and changes apolarization and/or an intensity of a radiation emanating from the μ-LEDwhen the radiation passes through the polarization element,

characterised in that

the polarizing element comprises a photonic structure.

655. μ-LED arrangement according to item 654, characterized in that

it is a three-dimensional photonic structure and/or that the polarizingelement is configured in the form of a layer which is arranged at leastin regions on the light-emitting surface.

656. μ-LED arrangement according to item 654 or 655, in which the μ-LEDis a vertical μ-LED with one connecting contact on opposite sides.

657. μ-LED arrangement according to any of the preceding items,characterized in that

the μ-LED, which is configured to emit light, in particular red, green,blue, ultraviolet or infrared light, which is irradiated into thepolarizing element, and that the polarizing element polarizes theradiation in an oscillation direction when passing through thepolarizing element.

658. μ-LED arrangement according to any of the preceding items, wherein

the polarising element has spiral and/or rod-shaped structural elements.

659. μ-LED arrangement according to any of the preceding items, wherein

the μ-LED comprises at least one converter element with a convertermaterial which, excited by excitation radiation emanating from theμ-LED, emits converted radiation.

660. μ-LED arrangement according to any of the preceding items,characterised in that

the polarizing element comprises at least one three-dimensional photoniccrystal.

661. μ-LED array according to any of the preceding items, wherein

the polarizing element comprises at least two two-dimensional photoniccrystals arranged one behind the other along a beam path of theradiation penetrating the polarizing element.

662. μ-LED array according to any of the preceding items, wherein

the polarizing element has at least two different polarizationproperties and/or degrees of transmission depending on a wavelength ofthe radiation passing through the polarizing element.

663. μ-LED arrangement according to any of the preceding items,characterised in that

the μ-LED has a converter element with a converter material which,excited by excitation radiation emanating from the μ-LED, emitsconverted radiation, and in that excitation radiation incident on thepolarizing element is polarized differently and/or absorbed to adifferent extent when passing through the polarizing element comparedwith converted radiation passing through.

664. μ-LED arrangement according to any of the preceding items, where

a three-dimensional structure of the polarizing element is at leastpartially incorporated in a semiconductor layer of the μ-LED adjacent tothe light-emitting surface.

665. μ-LED array according to any of the preceding items, which is athree-dimensional photonic structure and converter material is disposedin the three-dimensional photonic structure.

666. Method for producing a μ-LED arrangement having at least one μ-LEDwhich emits radiation via a light-emitting surface, and having apolarization element which adjoins the light-emitting surface at leastin sections and changes a polarization and/or an intensity of aradiation emanating from the μ-LED when the radiation passes through thepolarization element, characterised in that

an in particular three-dimensional photonic structure, in particular bytwo-photon lithography or glancing angle deposition, is applied to thelight-emitting surface of the μ-LED as polarization element and/or thephotonic structure is arranged in a semiconductor layer of the μ-LEDadjoining the light-emitting surface.

667. Method according to item 666, characterized in that the photonicstructure is dimensioned as a function of the wavelength of theradiation emitted by the μ-LED

668. Use of a μ-LED array according to any of the preceding items in adevice for generating three-dimensional images.

669. Use of a μ-LED array according to any of the preceding items,characterized in that

the μ-LED arrangement is used after one of the objects 654 to 665 forcomputer-aided generation of three-dimensional images for an augmentedreality application.

670. Optoelectronic component, in particular comprising a μ-LED array

at least one μ-LED which emits electromagnetic radiation via a lightemission surface, and

a photonic structure for beam-shaping of the electromagnetic radiationbefore it exits via the light emission surface, wherein the photonicstructure shapes the electromagnetic radiation such that theelectromagnetic radiation has a specific far field.

671. Optoelectronic component according to item 670, characterized inthat

the photonic structure is a one-dimensional photonic structure, inparticular a one-dimensional photonic crystal

672. Optoelectronic component according to item 670 or 671,characterized in that

the photonic structure is formed, in particular as a one-dimensionalphotonic crystal, in such a way that the radiated electromagneticradiation is at least approximately collimated in a first spatialdirection.

673. Optoelectronic component according to item 672, characterized inthat

a collimating optical system is arranged downstream of the light exitsurface, as viewed in the main radiation direction, the optical systembeing designed to collimate the electromagnetic radiation in a further,second spatial direction (R2), which is orthogonal to the first spatialdirection.

674. Optoelectronic component according to one of the preceding items,characterized in that

the photonic structure, in particular formed as a one-dimensionalphotonic crystal, is designed in such a way that a main radiationdirection of the electromagnetic radiation runs at an angle to thenormal of the light exit surface, the angle being not equal to zerodegrees.

675. Optoelectronic component according to item 674, characterized inthat

the photonic structure formed as a one-dimensional photonic crystal isarranged in a layer below the light-emitting surface, wherein theone-dimensional photonic crystal comprises a periodically repeatingsequence of two materials with different optical refractive indicesextending in a first direction, wherein the materials have abuttinginterfaces, which are not orthogonal but inclined to the light-emittingsurface.

676. Optoelectronic component according to one of the preceding items,characterized in that

the photonic structure is a two-dimensional photonic structure, inparticular a two-dimensional photonic crystal

677. Optoelectronic component according to item 676, characterized inthat

the two-dimensional photonic structure is designed such that theelectromagnetic radiation produces a defined, in particular a discrete,pattern in the far field.

678. Optoelectronic component according to any of the preceding items,characterized in that

the photonic structure is arranged in a layer, in particular asemiconductor layer, below the light emission surface, and/or thephotonic structure is formed in a semiconductor layer of theoptoelectronic emitter unit, and/or

the optoelectronic emitter unit comprises a converter material layer andthe photonic structure is formed in the converter material layer or in alayer between the converter material layer and the light-emittingsurface.

679. Optoelectronic component according to one of the preceding items,characterized in that the photonic structure, in particular instead of aphotonic

crystal, is a quasi-periodic or deterministically aperiodic photonicstructure.

680. Surface topography recognition system, with:

an optoelectronic device, comprising:

at least one optoelectronic emitter unit which emits electromagneticradiation via a light exit surface, and a photonic structure forbeam-shaping of the electromagnetic radiation before it exits via thelight emission surface,

wherein the photonic structure shapes the electromagnetic radiation suchthat the electromagnetic radiation has a specific far field,

wherein the photonic structure is a two-dimensional photonic structure,in particular a two-dimensional photonic crystal, and

wherein the two-dimensional photonic structure is designed such that theelectromagnetic radiation generates a defined, in particular a discrete,pattern in the far field, and

wherein said surface topography detection system further comprises

a detection unit, in particular with a camera, which is designed todetect the pattern in the far field

681. surface topography recognition system according to item 680characterized in that

it comprises an analysis device adapted to detect a distortion of thepattern with respect to a predetermined reference pattern.

682. Surface topography detection system according to item 681,characterized in that

the analysis means is adapted to determine a shape and/or a structure ofan object illuminated by the pattern as a function of the distortiondetected.

683. Scanner for scanning an object, comprising at least oneoptoelectronic component for one of the previous objects.

The description with the help of the exemplary embodiments does notlimit the various embodiments shown in the examples to these. Rather,the disclosure depicts several aspects, which can be combined with eachother and also with each other. Aspects that relate to processes, forexample, can thus also be combined with aspects where light extractionis the main focus. This is also made clear by the various objects shownabove.

The invention thus comprises any features and also any combination offeatures, including in particular any combination of features in thesubject-matter and claims, even if that feature or combination is notexplicitly specified in the exemplary embodiments.

1. An optoelectronic component, comprising: a μ-LED array with at leastone μ-LED which emits electromagnetic radiation via a light emissionsurface; a photonic structure for beam-shaping of the electromagneticradiation before exiting via the light emission surface, wherein thephotonic structure shapes the electromagnetic radiation such that theelectromagnetic radiation has a specific far field; and a collimatingoptical system arranged downstream of the light emission surface asviewed in a main radiation direction, the collimating optical systembeing configured to collimate the electromagnetic radiation in a secondspatial direction, which is orthogonal to a first spatial direction. 2.The optoelectronic component according to claim 1, wherein the photonicstructure is a one-dimensional photonic crystal.
 3. The optoelectroniccomponent according to claim 1, wherein the photonic structure is formedas a one-dimensional photonic crystal, in such a way that theelectromagnetic radiation is at least approximately collimated in thefirst spatial direction.
 4. The optoelectronic component according toclaim 1, wherein the photonic structure is formed as a one-dimensionalphotonic crystal, and is configured in such a way that the mainradiation direction of the electromagnetic radiation runs at an angle toa normal of the light emission surface, the angle being not equal tozero degrees.
 5. The optoelectronic component according to claim 1,wherein the photonic structure is formed as a one-dimensional photoniccrystal and is arranged in a layer below the light emission surface,wherein the one-dimensional photonic crystal comprises a periodicallyrepeating sequence of two materials with different optical refractiveindices extending in a first direction, wherein the two materials haveabutting interfaces which are not orthogonal but inclined to the lightemission surface.
 6. The optoelectronic component according to claim 1,wherein the photonic structure is a two-dimensional photonic crystal. 7.The optoelectronic component according to claim 6, wherein thetwo-dimensional photonic crystal is configured such that theelectromagnetic radiation produces a discrete pattern in the specificfar field.
 8. The optoelectronic component according to claim 1, whereinthe photonic structure is arranged in a first semiconductor layer belowthe light emission surface, and/or wherein the photonic structure isformed in a second semiconductor layer of an optoelectronic emitterunit, and/or wherein the optoelectronic emitter unit comprises aconverter material layer and the photonic structure is formed in theconverter material layer or in a layer between the converter materiallayer and the light emission surface.
 9. The optoelectronic componentaccording to claim 1, wherein the photonic structure is a quasi-periodicor deterministically aperiodic photonic structure.
 10. A surfacetopography recognition system, comprising: an optoelectronic devicecomprising: at least one optoelectronic emitter unit which emitselectromagnetic radiation via a light emission surface; a photonicstructure for beam-shaping of the electromagnetic radiation beforeexiting via the light emission surface; wherein the photonic structureshapes the electromagnetic radiation such that the electromagneticradiation has a specific far field; wherein the photonic structure is atwo-dimensional photonic crystal; and wherein the two-dimensionalphotonic crystal is configured such that the electromagnetic radiationgenerates a discrete pattern in the specific far field; and a detectionunit comprising a camera configured to detect the discrete pattern inthe specific far field.
 11. The surface topography recognition systemaccording to claim 10, further comprising an analysis device adapted todetect a distortion of the discrete pattern with respect to apredetermined reference pattern.
 12. The surface topography recognitionsystem according to claim 11, wherein the analysis device is adapted todetermine a shape and/or a structure of an object illuminated by thediscrete pattern as a function of the distortion.
 13. A scanner forscanning an object comprising at least one optoelectronic componentaccording to claim
 1. 14. A μ-LED arrangement for generating a pixel ofa display, comprising: a flat carrier substrate; at least three μ-LEDswhich are arranged on a mounting side of the flat carrier substrate,wherein the at least three μ-LEDs are adapted to emit light of differentcolor transverse to a carrier substrate plane in a direction away fromthe flat carrier substrate; a flat reflector element spatially arrangedon an assembly side relative to the at least three μ-LEDs and configuredto reflect light emitted by the at least three μ-LEDs in a direction ofthe flat carrier substrate; wherein the flat carrier substrate is atleast partially transparent so that light reflected from the flatreflector element propagates through the flat carrier substrate andemerges at a display side of the flat carrier substrate opposite themounting side; and wherein a photonic structure is incorporated in or onthe flat carrier substrate, with first and second regions with differentrefractive indexes, wherein a converter material forms one of the firstand second regions and is configured in such a way that radiation isemitted as a directed beam of rays.